I’ve mentioned this before in previous discussions, but one thing natives don’t seem to realize is that assimilation can never be instant. You always carry with you a part of your past. Full assimilation takes generations, usually three, at which time the original immigrant’s culture is all but lost.

1) Immigrant arrives, sticks mostly with their native culture/language/etc.
2) Immigrant’s children are “inbetweeners.” They have one foot in each culture, speak both languages and have embraced their new culture, but still think fondly of their parents’ culture.
3) Immigrant’s grandchildren are fully assimilated. Most of their grandparent’s language/culture is lost. 100% KFC/Taco Bell/Justin Beiber/America Fuk Yah!

Anecdotally I’ve seen this in many immigrant families, no matter where they are from (China, Mexico, etc). I see grandparents (original immigrants) who can’t communicate with their grandchildren due to the language differences. And the grandchildren look at their grandparents as a relic from another world to the point of being embarrassed that their grandparents don’t speak the language or eat “weird non-American food.”

This is why I believe the call for instant assimilation is unwarranted. It will happen naturally over time. It always has and always will.