I agree that Americans for several generations love to talk about their genealogy,,,,1/16 this, 1/8 that.  and in the first few generations may stay close to one of their countries of heritage, due to relatives they may know, soccer teams they may follow.  and then they have to pick which soccer team they like best,,,because they're half, something, and 1/4 something else, and then again.  it's all part of the melting pot effect in America.  but I didn't take the hyphen-American comment to mean that at all,,,but rather the opposite, that Americans stay divided,,,which they don't.

I guess my experience in Chicago and California is that these enclaves break down over a generation or two.  The German area in Chicago I believe is now Latino, with people moving out to the suburbs, or just marrying and moving.  In California I live in an area that is 40% Asian (lots of countries when I say Asian) and 60% everything else.  However the various China town areas do seem to maintain their Asian roots--but some of that seems business related.  Like in that area in London just south of Soho,,,very Chinese/Asian it would seem, and everyone knows where to go to get various varieties of Chinese food.