Nukes have a fixed lifespan. The rockets may still work, but the bombs won’t be fully functional certainly. They’ll probably still explode though. Explosives usually get more dangerous, not less over time. Another thing. Assuming this civilization surpassed us, and they’ve somehow constructed indefinite lifespan antimatter bombs for some reason. The world of kino’s journey is so insanely huge. It’s actually kinda crazy. Remember, kino has been traveling most of her life. She hasn’t circumnavigated the world despite that, or generally even crossed over her own path(as far as we know) the world is massive.(I believe this is part of the reason why globalization isn’t a thing) I’m not sure even a nuclear armed country could end the world. Do a lot of damage, yes, but there is probably a limit