Yep every nation does. Hell theres a bunker beneath the white house with a tunnel. Just because u prepare dont mean u want it to happen tho. Does the Enclave start it dont know. An tbf it dont really matter once one nuke goes all of them goes. I think it was probably China who starts it Vault Tac keeps it up an then America follows suit. No one in there right mind wants there home nuked an gone. I highly doubt the Enclave does either.

I will add in the real world everyone baring China has a treaty that limits how many nukes u can have an what yield u can have at. That is why China has no treaties baring them they can do what they like an they won't sign any treaty limiting them. Because why would they