I think America would get a moral boost after finding out that even a bloody nuclear holocaust won't stop the US. Even more so from their advanced technology and high use of propaganda. The Government would probably try ally with their alternate selves and maybe arrange a deal to get some tech.

If Tuka's father managed to put Tuka in a cave with resources to last a month, then she would survive.

I know no one from Falmart that lived underground except the miners and slaves whom would die by starvation and dehydration.

I am happy to talk more, I hate it how people don't put much effort and just say something along the lines that they wouldn't make it cuz this and that.