Actually I would like it placed outside US for once, like somewhere in Europe. The game lore barely talks about outside the US and China, and all we know is we hit China with tons of bombs and a few invasions I think... I guess... cant remember. All I can remember about Europe is they've been fighting with the US for its oil embargo before the bombs dropped, although armed conflict I can't remember. Maybe. Perhaps the place has suffered from harsh winter and its basically a barren land now... no super mutants though unless they went and built boats made out of human bones... oh hey I can imagine that.
If it must be in the US, well maybe Florida. Just think about it.
Fallout: Vice City... Wasteland.
...sorry, just had it stuck on my head seeing wastelanders and ghouls with swimsuits getting tanned in the beautiful radioactive beaches of sunny Miami.
Another one is maybe New York, although it has to be a frozen wasteland by now.
...maybe they will go tropical and go to South America?