You know, having a lot of a critical resource the US needs is not exactly an enviable position to be in.
The US as a whole has plenty of water, forever -- you could divert 10% of the Mississippi to the West and solve the water crisis. But you can't, because there's a mountain range in the way. Pumping and canals are VERY expensive.
Canada is even further away.
Everywhere that's not green is where humans won't be able to live by the end of the century.