See Immigration & The American Future, for a more in depth discussion of immigration issues.
On the purely political front, you need to consider, also, not only the general immigration and ethnic issues, but the vulnerability of people to demagoguish manipulation. As long as we have universal suffrage--or something very close to it--one has to consider questions of how well any group may be expected to exercise the suffrage from an American standpoint.
You are dealing with people who have a different set of images with which they identify. They are not primarily the images of Western Civilization, nor the more recent images of the Founding Fathers, and the pioneer settlers of the United States. When the chips are down, this differences in the images with which one identifies can be crucial--and would be crucial, even if the people involved had ever displayed the same capacity for participation in political self-government as the early Americans. (I do not find any evidence in Mexican History to suppose such an equivalent capacity; do you?)
As an American Conservative, I am devoted to preserving the very unique ethos of American civilization. That is a lot more complex than simply looking for work and a higher standard of living.
William Flax Return Of The Gods Web Site
Yeah, yeah, all Europeans and everyone else understands the American ethos but Hispanics don't. Whatever. Fantasy world.