Adapting to conservative, Protestant Christianity? I'm a liberal Lutheran. Am I properly "assimilated"?
Becoming a Republican? I'm a liberal Democrat. Do I need to be "shown the door"?
Becoming "an American"? My paternal grandmother's ancestors were Cherokee Indians. They were "removed" from Georgia after 19th century Americans deliberately broke every treaty they had with the Cherokees, and sent packing to Oklahoma where they "got" to live on reservations (but hey, they got the vote in 1948!).
My paternal grandfather's ancestors were German, some of whom were Amish. We still have clusters of blood relatives in northern Indiana who speak German and refuse to use electrical appliances. Do THEY need to leave?
My maternal grandparents were French (thank you, God!

) Since our "official" policy is to "hate the French" since they wouldn't support our invasion of Iraq based on our insistance that Saddam was hiding weapons of mass destruction which he intended to use on us at any second (and it turned out the French were right about this, after all), do WE need to leave?
Pray tell: exactly WHAT is "American culture"? Granted, I grew up in the Paleozoic Period of the 1950s and 1960s when dinosaurs roamed the earth, oil was being created and the Beatles and the Hermans Hermits were popular -- but I seem to remember that Americans are described as "a melting pot of different cultures" in a land of "equal opportunity for all".
Surely things haven't changed THAT much in 40 years...