This is actually quite true. Even Canada is quite "weird." It isn't, really, but it is a different country. I remember in grad school a friend from Canada describing all the little ways the US was "weird" (different) to her, and it was fairly enlightening, especially as if you're a Canadian without an identifiable accent nobody knows you're a strange in a stranger land when you fail to understand how to navigate things like the post office.
But foreigners are just people and many Americans tend to think of them as Martians, instead of just people who grew up with somewhat different cultural backgrounds, traditions, customs, and expectations.