Back then if you did not assimilate you were not just looked down on severly by society but banks could decide against giving you a loan, neighbors would choose to not be friendly if you could get into their neighborhood, schools woulld not treat children equally, etc. There are a lot of anti -discriminatory laws today that weren't there back then so it was in their best interest to assimilate as quickly as possible. Plus there was a pride to be "American." Today however there is cat food labeled in spanish, Home Depos have spanish signs if you do not know english, lots of government forms including drivers licenses and irs forms etc are in any native language, causing society to be both lazy in their new homeland Furthermore it is acceptable in society to be "cultural" by yearning for their homeland, and wanting to display their cultural pride.
Well, the immigrants' situation has changed. Their fathers immigrated to America because of a bad political situation, poverty, famine(well maybe not famine), and because America was the land of the future and of endless possibilities. Today their countries have become stable and wealthy countries, and add to that a bit of good old fashioned nationalism and there you have it!
And you aren't racist, you are talking about nationalities not races.