You don’t destroy America to prop up another country. Illegal immigration has wrecked hundreds of towns all across America and it is getting worse every day.
They think they have propped up the economic engine of America and headed off even bigger problems. A few small-towns suffer changing demographics? Just collateral damage - can't be helped.
Like I said - Bush isn't malicious or stupid, he just made a poor judgment call (with, I suspect, CIA advice) that a few murders in small-town America are better than having investment bankers jumping out of windows on Wall Street and a bloodbath in Mexico City.