So you would see it as a question of what might be called dilution, or the lack of it?

To achieve several generations without any intake of 'outsider' blood suggests that there must be a big community to start with and a ghetto-like separation from other groups. Given such conditions it is less surprising that succeeding generations should still identify with their place of origin

In the past I have generally viewed the States as the proverbial melting pot, but I am beginning to see it more as a number of quite distinct cultural/national/religious groups living alongside each other, with just a bit of blurring at the edges. Is that how others see or experience it?

Regarding the future, will more blurring eventually wipe out the separate groups, and if so about how many generations would you expect it to take?