It's what happened to Rome as well. They let in hundreds of thousands of 'barbarians', (foreignors), to work the farms and become soldiers. By the time they were attacked by the the rest of the 'barbarian' world it was too late to defend themselves, they had already been infiltrated and weakened, and the decadence was too much to overcome. History is definately repeating itlself in our own times, in our own country.
It's surreal, watching what's happening, understanding the historical analogs, knowing the eventual outcome...and still going about day-to-day life, grocery shopping, doing whatever. Very two-headed. I suspect that there will be quiet mass movement to certain geographic regions in the country, and unspoken boundaries will become more pronounced and enforced as the years pass. People who take the time to move en masse across the country will be less PC about what goes on in their new digs.
You can forget Calif, it is already a defacto Mexican state, but we might be able to hang onto Texas if we can elect leaders that will defend the nation against this horde of invaders.