If it’s anime/manga, absolutely either Japan, Europe or Hawaii. If it’s a cartoon and I know what country it originates from, that country. Otherwise I’ll assume it’s some fictional place that could be anywhere if it isn’t specified.

Good question. Really depends on what it is, I think. I just watched the movie Melancholia which is pretty ambiguous about its setting. I was wavering between US and UK based on the accents, but I think in the back of my head I kinda assumed vaguely East Coast -ish.

I’m primarily a fantasy reader. I never assume anything related to time or place, lol.

I assumed it was set in the United States until the main character went to London.

I’d assume that London was a city on the Thames bridged by Blackfriars Bridge in the UK.

But you never know, because it might be that London was a city on the Thames bridged by Blackfriars Bridge in Canada.

Truthfully, I don’t think about it much unless the media bothers to bring it up. If it’s not a particularly strong element of the narrative, I’m not concerned about it.

As a kid, in the UK, back in the '70s, I was watching Roots and was wondering why they were so keen to get to Scotland. I eventually realised that this was set in the US, of course, and the north there was different.

So I suppose that was my default then but, these days, I typically find myself trying to work out exactly when and where a thing is set, if it isn’t obvious, automatically - before I actually settle into the plot or anything.

Frankenstein (the book) is all over the place. Haven’t seen the new movie yet so I don’t know what settings they use there.

https://www.sparknotes.com/lit/frankenstein/setting/

A lot of it depends on context. You’re not really told where the city in the Matrix is located, but based on the skyscrapers and freeways in part 2 it feels really LA-ish. Filmed in Sydney. But of course “The Matrix” has no physical location so it doesn’t matter.

If they speak english, I assume it’s in Vancouver