I agree that this isn't likely in the US. I don't like illegal immigration and believe that the government should be doing much more to stop it. But the truth is most of the illegals come to the US to work, and are too busy to get involved in "revolutionary" movements. The only significant movement for Atzlan is in the leftist universities. In fact I couldn't imagine any working immigrant hoping that their area becoming a Mexican offshoot. If there was such a new country it would be as horribly run as Mexico a third world hellhole that they risked their lives to escape. The main issue here is to ensure that assimilation is required and these intellectual eggheads are not allowed to spew their poison to young minds.
The fact is all of old Europe is far more racist than the US, and they have forced their immigrants into ghettoes where they are allowed to run wild.
Speaking as someone who has traveled to Europe and who does business there on a regular basis, you are absolutely correct. For all their kum-ba-ya multicultural platitudes and laws against "hate speech", Europeans are much more racist than Americans, even against law abiding tourists "of color" who have money to spend.
With the possible exception of Brazil, the US is the least racist country on the planet. Take a look at the average state legislature or corporate office in the U.S. and compare it to Europe, or even Latin America for further evidence.