When it starts to happen, one can only hope that we have leaders wise enough to procure some more (warm) territory for the United States.
What is the best candidate? Mexico.
Give them an ultimatum: stop violating our borders. If they reject such as resonable proposal (as they will undoubtedly do, since history tells us that tyrannical government are rarely "reasonable"), we invade and take half of their damn country.
Now, being a compassionate and just people, we should compensate the oppressed Mexican peasants for any "inconvience" they will incur as a result of the previously mentioned events.
I say we give them the entire Northeast United States, and build a wall between that region and the "new" US. This could be done under the guise of "border security", but the REAL reason for it should be to keep the US-born northeastern liberals from leaving the region and contaminating the rest of us.
This solution would kill two birds with one stone.