There was a post on r/askanamerican just the other day, by a guy living in Eastern Europe who has a fun backpack (it looks like a reeses cup package with a bite taken out of it!) and said he constantly got compliments on it from American tourists
And he was like...are all of you like that? You say nice things to total strangers as if you're life-long friends??
And the entire comment section was like: Yup. Absolutely. This is 100% a thing we do.
And someone looked up a picture of the backpack and shared it and we were all like OMG THAT IS AN AMAZING BACKPACK yeah if I saw someone in any city on earth wearing that thing I would in fact say something.
Sometimes posts on that subreddit are a trash fire, but we were all so happy to talk about times we've told strangers compliments or been complimented by strangers.
And genuinely, it's one of the few things that makes me proud to be American. Like. We have a reputation for telling total strangers when we like something they're wearing/doing. And we mean it, every single time!