I will take your word that there are schools that teach Chinese martial arts in the USA that don't use rank but from what I've seen, some schools that in the past haven't used rank are starting to. This one school that I visited in NYC that teaches the Eagle Claw system originally didn't have rank but ended up coming up with a ranking system that consisted of colored sashes where a black sash was the lowest rank and a white sash was the highest rank.
I wouldn't say that the need to be ranked is entirely an American thing or that wanting rank is a typical attitude in the USA, after all there are some combat sports, if not martial arts I would at least call them combat sports, that have a long history in the USA that traditionally haven't and to this day still don't have rank. American boxing and American wrestling for instance, typically don't have rank.