From the Life-Isn't-a-Snapshot-It's-a-Movie Department, we have this piece by Stephen Haber in today's Wall Street Journal ($):
The impact of immigration on American culture is not determined by what immigrants do, but by what their children and grandchildren do. Here the evidence is unambiguous:
The children and grandchildren of Mexican immigrants assimilate and move up the income ladder. Meticulous research by James Smith at Rand demonstrates that second- and third-generation Mexican-Americans quickly overcome the educational deficit faced by their immigrant parents and grandparents. As a result, they do not constitute a permanent economic underclass; they have been steadily narrowing the income gap with native-born whites.
Nor do they constitute a social and cultural group independent of mainstream America. The reason is clear: 80% of third-generation Mexican-Americans cannot speak Spanish. ...
Mexican Wave, WSJ, May 3, 2006, p. A14 (extra paragraphing added).
I can relate: On my mother's side, I'm a second-generation American, and so far as I know, none of my siblings or cousins or I know more than a few words of our grandparents' native language. (Actually, one cousin is fluent in it, but she learned it at school.)