I think we get this a lot as Americans because we are such a huge cultural power with our movies, music and software. (and pizza). But like, there are definitely enormous cultural differences between Northern and Southern Italians, or N/S Vietnamese, or like, the 500 different cultures in India... we're sort of blind to it until we go somewhere because no matter where you are, you just get the summary of everywhere else.
I see tons of online comments generalizing about California or the West Coast (I’ve been guilty of this generalization myself), but after living here for the past 8 years I’ve learned otherwise. I will also refer anyone who wants to lump the whole coast together to Oregon’s legacy as a self-proclaimed “white state” [0].
It turns out that making accurate generalizations about millions of people is hard, and if you’re committed to doing it anyways then you’ll just end up with cliches and platitudes.
[0] https://history.howstuffworks.com/historical-events/racial-h...
Bingo. If one hasn't spent serious time in at least 4+ states, I don't think they ever really get an idea of how differentiated American cultural norms really are. "Americans are ______" is about as descriptive a statement as "Left-handed people are _____" - there's just toooo much variance for it to be a useful observation.