The US is is geographically larger than Europe, has a comparable number of people, and is arguably as diverse.
Yes, it looks like we speak the same language, but the diversity in "American" is at least as broad as the difference between the middle of "American" and "received English". (Yes, I'm aware that there's a lot of diversity in UK English.)
Yes, Americans mostly watch the same TV, but our exports and castoffs are not unknown in Europe.
America is not as lingusitically diverse as Europe. The difference between 2 American english accents might be similar to the difference between 2 English accents, but there are dozens of languages in europe. You're comparing the whole of the US to one part of EU.
Yes, it looks like we speak the same language, but the diversity in "American" is at least as broad as the difference between the middle of "American" and "received English". (Yes, I'm aware that there's a lot of diversity in UK English.)
Yes, Americans mostly watch the same TV, but our exports and castoffs are not unknown in Europe.