The United States of AMERICA. End of discussion, thread over, everybody go home, nothing to see here, folks! If you want a post-apocalyptic version of your country, make your own PA game series!
Savannah Georgia, New Orleans, Or some were in the great plains like South Dakota or upper Minnesota
New Orleans maybe, Georgia would be boring, South Dakota would depend on where but little of it would be very interesting as far as realistic man-made content, and Minnesota would be mind-numbingly dull.
I doubt a nuclear war could make the home of A Prairie Home Companion any less boring.