When I first read the Stratfor article linked above five years ago, it fundamentally changed the way that I looked at immigration in America. Here's a quote.
"Sicilians might remember Sicily, they might harbor a cultural commitment to its values and they might even have a sense of residual loyalty to Sicily or to Italy — but Italy was thousands of miles away. The Italian government could neither control nor exploit the migrant’s presence in the United States. Simply put, these immigrants did not represent a geopolitical threat; even if they did not assimilate to American culture — remaining huddled together in their “little Italys” — they did not threaten the United States in any way. Their strength was in the country they had left, and that country was far away. That is why, in the end, these immigrants assimilated, or their children did. Without assimilation, they were adrift....
"The immigration debate in the U.S. Congress, which conflates Asian immigrations with Mexican immigrations, is mixing apples and oranges. Chinese immigration is part of the process of populating the United States — a process that has been occurring since the founding of the Republic. Mexican immigration is, to borrow a term from physics, the Brownian motion of the borderland. This process is nearly as old as the Republic, but there is a crucial difference: It is not about populating the continent nearly as much as it is about the dynamics of the borderland."
I recommend Stratfor to people all the time (and no, I don't receive anything for doing so, nor do I work for them). This article in particular is refreshing in its clarity and precision. I need more of that, daily; I think we all do.