I know this is from awhile back, but that's actually not true. In the US, we're mainly an exporter of resources. We import stupid crap like plastic toys and junk. Besides, it's not like those resources are gone. They're in the buildings, machines, and landfills all around. It would be pretty easy to scavenge building materials without having to go into one of the thousands upon thousands of mines we have.
I know this is only a game - so the following (out of topic) is written mostly because I found this discussion interesting.
My point was that with full scale nuclear war all transport networks, mines, factories etc. will be destroyed. So even there is gold and oil in Alaska it doesn't help much in New Vegas .... There will not be much flora or fauna left - thanks to nuclear winter and after that UV (ozone layer will be wiped away). What will be left is cockroaches, viruses, bacteria and might be rats ...
So before fauna and flora can recover (to level we are used to) - it needs a lot of evolution and birth of species.
When people can hardly get their food - they don't focus to anything else than getting it - it means knowledge and civilization will just disappear during first decades. So will disappear most of machines and electronics. If a car stays out for 50 years - there is not much left of it ... especially after acid rains ... and the same formula goes pretty much for everything - even for buildings.
Even e.g New Vegas didn't get direct hit - its inhabitants needs to be sheltered over nuclear winter (-22F and totally dark period for one Year) - and if they survive it, they can't be in direct sun light for years. Afterwards there will not be left anything to farm. So first decades they are searching rats and cockroaches for food. They are also very sick - a lot of cancer - their children will be mostly mutated etc. etc..
From that kind of situation it is hard to believe in 200 years they reach an technology level close to present.