I mean, the east would be tank land, flat, open terrain. I can see someone scavving russian and German tanks. Like Leopard 2a4/5s or some T-80s/90s. Unless you were virtually untouched by the bombs I don’t see how people can progress past what was there.

IMHO- I think your tech should depend on where you are and what was there before you. For example, if you take the Pacific, you should expect to find a lot of ships that could be repaired and canabilized for parts. Likewise for your land powers ( Germany, France) I would expect to find main battle tanks. 

In terms of retaining information, yes some would be lost but a good majority of it could still be found and retained. In the nuclear reactor example, you might not be producing nuclear scientists but you will have people who know how and  a reactor works enough to use one.