Well...yes, if the infrastructure can be destroyed.Nomen Nescio said:On a side note, don't want to crush your Falloutesque dreams, but I've read somewhere that at this point no country is prepared to cope with a loss of it's electricity infrastructure, as you can't produce new components or repair old ones without electricity itself. You can't get fossil fuels without it, or even dream about maintaining a food supply chain (cities would have to die out of starvation). Domino effect all over the place.
All this considered, I think only the meanest and most ruthless would survive. Of course also smart enough to realize he/they won't survive only by plundering - hello feudalism or even slavery.
In many nations that's going to take a lot of doing, with important parts scattered over wide areas.
Secondly, what about neighbouring nations? Plenty of reasons why a neighbouring country not so badly off would want to help.
As an aside, during (at least part of) the Cold War, the USSR had submarines that wouldn't take part in WW3, they'd wait a year, surface, launch spy satellites, find out what was being rebuilt and hit it again.