Really?
Take a look at those rallies. Those are Mexican flags being waved around, not American flags. It's Spanish being spoken, not English. The nationalism in their hearts is not for this country, it's for Mexico. Cinco de Mayo is a bigger deal to them than July 4th. If you can't see that, then you are part of the problem.
As far a secession, A very large part of our population can't seem to stomach 2,400 casualties in Iraq. I seriously doubt this country's ability to fight a war on our home soil on the scale of 1860-65. Especially with millions of enemy agents in our midst.