7 is correct
9 is correct so far.
11-13 are correct.
14. The first one is incorrect, the other two are correct.
15. Is correct so far.
 

Don't know the answer to your question but 6 is correct.

1. Two municipalities, one in the United States, the other in the United Kingdom, share a celebration each August 9 whose name makes it sound more dreary than it really is. Name the day and the municipalities.

2. Name the three waterfalls at the Niagara Falls ON and Niagara Falls NY border, and indicate which of the three touches the Ontario side.

3. Which controversial historical figure has a larger than life statue in the Fremont area of Seattle?

4. What is the capital city of Vanuatu?

5. In which park can you find the Vancouver Aquarium?

8.What is the largest island between Vaudreuil-Dorin and Saint Anne-de-Bellevue, Quebec, and what bird is its name French for?

9. Easter Island is part of which country, and what is the island's most common alternative name [Rapa Nui]?

10. In which city can you find a cat museum, torture museum, marijuana museum, and eye glasses museum, as well as two erotic museums?

14. Which three regions make up Oceania? [?, Micronesia, Polynesia]

15. Which country is in between Switzerland and Austria [Liechtenstein], and what is its capital?

[Loki's add:]
16. Which three locations in which three countries voluntarily formed the "Trinity of Tedium"?
 

10 is incorrect.

1. Two municipalities, one in the United States, the other in the United Kingdom, share a celebration each August 9 whose name makes it sound more dreary than it really is. Name the day and the municipalities.
The US one is an unincorporated community, the UK one is a village.
The US one is in Oregon, the UK one is in Scotland

2. Name the three waterfalls at the Niagara Falls ON and Niagara Falls NY border, and indicate which of the three touches the Ontario side.
The latter touches both sides and one of its two names (I'll accept either) relates to its shape as a result. The other two are only known by one name each.
The smallest one is named after a wedding accessory for women, the medium sized one has the most US sounding name, and the largest is named after something you can find on a ranch.

3. Which controversial historical figure has a larger than life statue in the Fremont area of Seattle?
The figure is not from the Americas.
He started a revolution in his country.

4. What is the capital city of Vanuatu?
Two word name
First word sounds like a place you might find ships, second word sounds somewhat like a type of municipality.

5. In which park can you find the Vancouver Aquarium?
Vancouver's most famous park.
A Canada-US sports trophy was named after the same person as the park

8.What is the largest island between Vaudreuil-Dorin and Saint Anne-de-Bellevue, Quebec, and what bird is its name French for?
Hyphenated word, with the part after the hyphen being the French word for the bird
The bird can mimic human words

9. Easter Island is part of which country, and what is the island's most common alternative name [Rapa Nui]?
Most of the rest of the country is on a continent.
The continent is mostly in the southern hemisphere, as is Easter Island

10. In which city can you find a cat museum, torture museum, marijuana museum, and eye glasses museum, as well as two erotic museums?
Not a city in the Americas.
Somewhere in Europe

14. Which three regions make up Oceania? [?, Micronesia, Polynesia]
Remaining name sounds similar to a word related to skin colour.
Shares the last five letters as the other two, so zuckyd1 wasn't that far off.

15. Which country is in between Switzerland and Austria [Liechtenstein], and what is its capital?
One word
Five letters

[Loki's add:]
16. Which three locations in which three countries voluntarily formed the "Trinity of Tedium"?

 

9-10 are correct. 14 is incorrect but you have the right idea. Not pigment but a similar kind of word, minus part of its last syllable. Amsterdam of course is known for letting people smoke pot legally, particularly when smoked in coffee shops, and its two erotic museum are in its Red Light District, known for being safer than most for sex trade workers.

Loki wrote:

I've got the answer to #1, but it also answers my own question. 
1. Dull and Boring. The Scottish town of Dull in Perth and Kinross is twinned with Boring, Oregon. But in 2013 they added in a third location, Bland in New South Wales, Australia, forming what is now known as the Trinity of Tedium. 

I did start to suspect there might be that overlap but I didn't want to say so and ruin my original question, which is what actually gave me the idea for the quiz. The day appears to have different names, but as of 2022 the signage in Boring still called it Boring and Dull Day. Speaking from what I know firsthand, there's a Boring Garden Center, Boring Mini-Storage, and Boring Bark and Landscaping. The door on the Shell gas station used to say Boring Shell. A now-closed pub was called the Not So Boring Pub. The local branch of the Clackamas Fire District used to be called Boring Fire District and their vans used to read Boring Fire. But my favourite is that they have a Boring Middle School.

Larger versions of the below here:
https://www.flickr.com/photos/24917258@N05/20905787744/
https://www.flickr.com/photos/24917258@N05/52351969357/
https://www.flickr.com/photos/24917258@N05/21537110621/
https://www.flickr.com/photos/24917258@N05/9718716521/
https://www.flickr.com/photos/24917258@N05/36140836213/






More photos upon request. These were all taken by me.
 

More clues. For some I'll declare final clue because there isn't much more to say:

2. Name the three waterfalls at the Niagara Falls ON and Niagara Falls NY border, and indicate which of the three touches the Ontario side.
The latter touches both sides and one of its two names (I'll accept either) relates to its shape as a result. The other two are only known by one name each.
The smallest one is named after a wedding accessory for women, the medium sized one has the most US sounding name, and the largest is named after something you can find on a ranch.
The smallest one is two words before Falls and is something the woman actually getting married might wear in the upper half of her body; the medium sized one is one word before Falls; and is a very common descriptor for the US; and the largest is one word before Falls, and for the answer I'm pushing the most, can also be used in a game

3. Which controversial historical figure has a larger than life statue in the Fremont area of Seattle?
The figure is not from the Americas.
He started a revolution in his country.
The country is somewhere in Eurasia

4. What is the capital city of Vanuatu?
Two word name
First word sounds like a place you might find ships, second word sounds somewhat like a type of municipality.
FINAL CLUE: Both words four letters.

5. In which park can you find the Vancouver Aquarium?
Vancouver's most famous park.
A Canada-US sports trophy was named after the same person as the park
Park has a beach where West Vancouver and North Vancouver can be seen

8.What is the largest island between Vaudreuil-Dorin and Saint Anne-de-Bellevue, Quebec, and what bird is its name French for?
Hyphenated word, with the part after the hyphen being the French word for the bird
The bird can mimic human words
If you take the French word for the bird, and subtract once the duplicate letter, you get the surname of a former US Presidential candidate.

14. Which three regions make up Oceania? [?, Micronesia, Polynesia]
Remaining name sounds similar to a word related to skin colour.
Shares the last five letters as the other two, so zuckyd1 wasn't that far off.
FINAL CLUE: Four letters before the "nesia"

15. Which country is in between Switzerland and Austria [Liechtenstein], and what is its capital?
One word
Five letters
FINAL CLUE: Has a postage stamp museum

5. Stanley Park

Here are the answers:

2. Name the three waterfalls at the Niagara Falls ON and Niagara Falls NY border, and indicate which of the three touches the Ontario side.
The latter touches both sides and one of its two names (I'll accept either) relates to its shape as a result. The other two are only known by one name each.
The smallest one is named after a wedding accessory for women, the medium sized one has the most US sounding name, and the largest is named after something you can find on a ranch.
The smallest one is two words before Falls and is something the woman actually getting married might wear in the upper half of her body; the medium sized one is one word before Falls; and is a very common descriptor for the US; and the largest is one word before Falls, and for the answer I'm pushing the most, can also be used in a game
Looking from Ontario to New York, left to right: medium one (descriptor mostly used for the US but could also be used for a larger region), smallest one (the woman getting married wears the namesake on her head), largest one touching the Ontario side (this one has a curve)

Medium sized waterfall [medium one (descriptor mostly used for the US but could also be used for a larger region)]: American Falls
Smallest waterfall [(the woman getting married wears the namesake on her head)]: Bridal Veil Falls
Largest waterfall [largest one touching the Ontario side (this one has a curve, named after something you can find on a ranch, also used in a game)]: while I would also accept Canadian Falls, the most common name is Horseshoe Falls

3. Which controversial historical figure has a larger than life statue in the Fremont area of Seattle?
The figure is not from the Americas.
He started a revolution in his country.
The country is somewhere in Eurasia
There used to be a fast food franchise near the statue, a bit ironic as the subject wasn't all that fond of capitalism

Vladimir Lenin

4. What is the capital city of Vanuatu?
Two word name
First word sounds like a place you might find ships, second word sounds somewhat like a type of municipality.
Both words four letters.

Port Vila

8.What is the largest island between Vaudreuil-Dorin and Saint Anne-de-Bellevue, Quebec, and what bird is its name French for?
Hyphenated word, with the part after the hyphen being the French word for the bird
The bird can mimic human words
If you take the French word for the bird, and subtract once the duplicate letter, you get the surname of a former US Presidential candidate.
Some of the birds can be quite colourful

Île Perrot, the bird being parrot. There's some quirky naming aspects: Île Perrot (the island) has three municipalities: Pincourt, L'Île-Perrot (the municipality), and Notre-Dame-de-l'Île-Perrot. However L'Île-Perrot (the municipality) spans part of Île Perrot (the island), as well as the smaller islands of Île Claude and Île Bellevue)

14. Which three regions make up Oceania? [?, Micronesia, Polynesia]
Remaining name sounds similar to a word related to skin colour.
Shares the last five letters as the other two, so zuckyd1 wasn't that far off.
Four letters before the "nesia"

I was trying to allude to "melanin", so Melanesia

15. Which country is in between Switzerland and Austria [Liechtenstein], and what is its capital?
One word
Five letters
Has a postage stamp museum

Vaduz
 

Next set also on location, but focusing on the Pacific Northwest, so southern British Columbia (BC), Washington (WA), Oregon (OR). At least part of Idaho is also in the region but I don't have enough knowledge of that state to do questions. A few of the questions arguably have a slight pop culture aspect, but well on the periphery so it's probably okay.

1. For British Columbia, Washington, and Oregon, name their respective capitols.

2. Until it was shut down indefinitely due to COVID, what was the only Washington State Ferries stop not in Washington State?

3. What store in which city can you find the Rubber Chicken Museum and the World's Largest Rubber Chicken?

4. In which city can you find the World's Tallest Tin Soldier?

5. What is the name of the world's smallest park and in which city can you find it?

6. In Carlsborg, WA, there is a private road called My Way. How does its location make it a pun?

7. Which beach-sounding municipality is just south of Boring, OR?

8. In which business in which city can you find a vacuum museum?

9. Which light rail transportation in Seattle has just two stops?

10. Which municipality unfortunately made the news when it was when it was discovered that some of its residents were engaging in what they considered to be romance with horses? I'm probably going to have to be a bit more vague with some of the clues than I would be for the other questions.

11. What is the largest municipality in Greater Victoria?

12. What are light rail trains in Greater Vancouver, BC called?

13. Where can you find the last Blockbuster Video?

14. Which Seattle landmark can you find under a bridge?

15. Which municipality is directly north of Portland, OR?

16. Victoria, BC is on what island?

17. Victoria, BC's Inner Harbour has two ferries going to Washington State. What are the two municipalities they go to, or if you prefer, come from? That is, each ferry stops at Victoria and only one other municipality.

18. In which district in Vancouver can you find a steam clock?

19. The Old County Market is known for having multiples of a particular type of animal on the roof. Which animal are they and which municipality?

20. In which municipality can you find the headquarters of Amazon?

21. In which municipality can you find the headquarters of Microsoft?

22. In which municipality can you find the headquarters of Fantagraphics?

23. In which municipality can you find the headquarters of Dark Horse Comics?

24. Which video company known for distributing obscure, oddball movies/short/trailers from past eras is based out of Seattle (and previously Lynnwood?

1. Salem is correct for Oregon.
6 isn't related to Sinatra.
20 is correct.
21 is incorrect but can be accessed from Seattle by public transit; currently just buses but soon light rail.
22 is incorrect.
23 is incorrect but can be accessed from Portland by public transit (you can take a bus but light rail is a lot faster).
24 is correct.
 

1. Spokane, Washington?
6. Is My Way located near a highway?

1. For British Columbia, Washington, and Oregon [Salem], name their respective capitols.
Not Vancouver for BC nor Seattle for WA
BC: think British royalty. WA: think Greece

2. Until it was shut down indefinitely due to COVID, what was the only Washington State Ferries stop not in Washington State?
Not Greater Vancouver
Somewhere in BC

3. What store in which city can you find the Rubber Chicken Museum and the World's Largest Rubber Chicken?
Not Powell's Books
Store is name of person and is located in WA

4. In which city can you find the World's Tallest Tin Soldier?
Not Portland
Not the main city, but part of a Greater _____

5. What is the name of the world's smallest park and in which city can you find it?
Arguably despite the efforts of some past provincial governments, the world's smallest park is not in BC
Major city. For name of park, think "grinder terminates".

7. Which beach-sounding municipality is just south of Boring, OR?
Not Seaside.
Location has a [municipality name] Chainsaw, [municipality name] Bicycle, and [municipality name] Liquor, and in all three cases the municipality name might put you off the purchase.

8. In which business in which city can you find a vacuum museum?
Not a business with additional locations **outside the Pacific Northwest**.
Franchise in the general area, with this branch in a major city.

9. Which light rail transportation in Seattle has just two stops?
Not the Sounder train.
One stop takes you almost right to the Space Needle

10. Which municipality unfortunately made the news when it was when it was discovered that some of its residents were engaging in what they considered to be romance with horses? I'm probably going to have to be a bit more vague with some of the clues than I would be for the other questions.
Not in BC
The last syllable is something that some animals have but not horses.

11. What is the largest municipality in Greater Victoria?
Not Victoria proper.
First Nations sounding name,

12. What are light rail trains in Greater Vancouver, BC called?
Nothing that sounds like "subway".
Name suggests above ground, despite one of the lines being largely underground.

13. Where can you find the last Blockbuster Video?
Not in BC
Trying to guess this might drive you nuts. It might even...

14. Which Seattle landmark can you find under a bridge?
Nothing related to grunge music.
Consider works of fiction involving bridges.

15. Which municipality is directly north of Portland, OR?
Not an Oregon location.
Shares name with a much better known Pacific Northwest city.

16. Victoria, BC is on what island?
Not Victoria Island (and we hate it when people call the island that).
Shares name with a city not on the island.

17. Victoria, BC's Inner Harbour has two ferries going to Washington State. What are the two municipalities they go to, or if you prefer, come from? That is, each ferry stops at Victoria and only one other municipality.
Not Forks (sorry Twilight fans) or Port Townsend
One of the two locations is a major city, the other is two words and the second word is the same as the second word in a well known city in the US far south of the Pacific Northwest but still on the west.

18. In which district in Vancouver can you find a steam clock?
Not Granville Island
Think fuel

19. The Old County Market is known for having multiples of a particular type of animal on the roof. Which animal are they and which municipality?
Not horses
Location is hair item often found in bathroom, only with one letter duplicated. Trying to figure out the animal type might be very frustrating. It might even...

21. In which municipality can you find the headquarters of Microsoft?
Not Everett
East of Seattle but still greater Seattle.

22. In which municipality can you find the headquarters of Fantagraphics?
Not in Oregon
Major city.

23. In which municipality can you find the headquarters of Dark Horse Comics?
Not Beaverton.
While not in Portland proper, it's part of Greater Portland