A large number of Americans know how to work on cars, and Americans buy ammo. There will be plenty of both in a post-apocalyptic world.

If there is a total energy failure tomorrow, 1 million will die within 1 hour. 60% will die within 12 months. 90% will die within 24 months. So that means even MORE cars and guns for the survivors. Like myself. I want one of the new Dodge Hellcats and a trunk full of guns. I'll scare up my own freakin gasoline.