Yes, I'm sure all americans are the same to you, being from somewhere that's not america. I actually live in the US, and I've actually traveled around, so I feel that I have a better idea about it than you do.
I mean I'm just saying, it's much more likely that you're going to generalize all americans as the same (as you're doing) if you're an outsider who's never even been to america.
It's all a matter of relativity. When cultures are similar, a different culture can very easily see these as petty differences, but in reality although the differences are fairly minor, they are differences, and they do entail the cultures being different, especially tin the eyes similar ones.