Was first going to say Hawaii because it is so far out there. I mean, if you want to relax on the beach there are Caribbean islands that are much closer. The Florida Keys, etc, etc. But Hawaii is important as a strategic military base in the Pacific.
Alaska is removed from the Continental 48 but it has so many natural resources that it would be a loss to lose Alaska.
I'm going with one of the desert states, Arizona or New Mexico, take your pic. Sustaining the cities out in the desert are going to get much more difficult going forward too. Maybe we recreate Las Vegas somewhere else and give up Nevada. Yep, one of the 3 desert states would be my choice.