Things I wish non-American writers would stop doing: set novels vaguely in America for no apparent reason, and get all of the details wrong.
You can tell when a novel is set in a country that the writer is not particularly familiar with. I do not want to use Fifty Shades of Grey as an example, but it is such an obvious example that I feel it will illustrate my point quite well: it is set in America (I imagine because Twilight is set in America), but the author is English. The characters use phrases that are not used in America, because the author is familiar with how people speak in England. There are impossible uses of geography, because the writer does not know how long it takes to drive between, say, Portland and Seattle, because she lives in England.
Things do not ring true if someone is writing about a place they are not familiar with. I am Australian, and I have never been to America, and I can tell if you are writing a book about this place and you have not actually been there yourself. This is because I have consumed a lot of TV shows and books and movies and everything else that is set in or is about America ('consumed'. I just imagine myself eating DVDs like the Cookie Monster). There is an excess of novels and films and TV shows about America. That's okay. But that doesn't mean you have to set your book there, too, and please, not if you don't know a thing about the place. Then it's just awkward and factually inconsistent.
I am not saying that you are forbidden to write stories set outside of your country, but if you are going to please do it reasonably well. Maybe go to that country for a while, or get someone from that country to read your manuscript and correct you. Set it in a foreign country only if you can write it in a convincing and believable way. And don't set it in America by default if you are non-American. I mean, think about it. Do you not think we have enough narratives about America already? Try to bring something new to the table, please. (Example: Hollywood Ending by Kathy Charles. Australian writer! L.A. setting! But convincing and believable and very well-written, and it wouldn't work set anywhere else. Because the author wrote a novel about a place they love and are familiar with.)
And this is not just a problem with novels set in America. I don't want you appropriating other people's culture and writing a novel set in Imperial Japan if you don't know anything about Imperial Japan. Googling does not count. I REPEAT. Googling does not count. (At least not for very much.)
But this post is specifically about America because there are so, so many novels - particularly of the YA paranormal romance variety - that are set in a vague American setting for no reason. Also cultural appropriation is obviously a much more complicated thing which I do not feel informed enough about to write an entire post on it. Plus everyone writes novels full of white people, what is up with that? Let's talk about this later though. We're talking about badly evoked vaguely American settings written by non-Americans.
So, why are people doing this? Do supernatural creatures only exist in America? (Apart from a brief trip to Italy or Transylvania or wherever.) Does everyone just want their novels to become bestsellers in America, and think Americans will only read about America? Will Americans only read about America? I am sure Americans won't mind if we maybe don't Americanize (Americanise?) all of our culture.
IN CONCLUSION: don't be lazy and set your YA paranormal romance novel in Not-Forks-but-similar-to-Forks, USA, especially if you know as much about America as I do (i.e. not a lot, except for stuff from movies). Research! Maybe go there! Maybe consider bringing vampires to the Gold Coast, Aus! No, bad idea. Too sunny. Write about different places! But research them properly and thoroughly.