This is something I have been putting a lot of thought into lately. My wife and I have been fortunate to have lived in France, England and Spain over the past decade, as well as being regular visitors (+6x/year) to the United States.

The more places I see, the more I realize that the area of the world I grew up in, the interior of British Columbia, Canada or where my wife grew up in Alberta, Canada, are both better suited to handle the projected long-term adverse climate changes than anywhere else I've ever been.

With the use of greenhouses, their easy access to abundant fresh water and readily accessible energy I think they're both well-suited areas to long-term stability.