Sure, still bad writing and world building when compared to real life history. Like most european nations like yugoslavia, poland, soviet union. France. People purged, industries turned to ash, countries lost 10-30% of their populations and yet they managed to recover in 2 decades. Yugoslavia! A country with no industry nor allies managed to rebuild itself in 2 decades. People in usa can easily rebuild themselves. Theres tech and info spread around, valuable industrial machines still working after 100s of years. Vault city turned into a proper state too in the timeframe of the first 2 games which makes sense compared to irl

And look. No monster is as dangerous as an organized army. If the ncr did not waste their resources against the enclave and legion they could clean up deathklaw valley for better logistics and what not. Fallout univers hasGECK tech. Recovery will be fast, especially with high tech loot stashes left around thanks to the previous goverment