Stock up on gold, silver, pocket change (pennies and nickels), old car batteries, and scrap brass, preferably cartridge brass. Oh, and pick up a copy of “Machinery’s Handbook” to figure out what wonderfully nasty things you can make with all of those raw materials.
If a bunch of third world types can bash out AK-47’s in barns and caves, just imagine what some ambitious educated machinists in the US can come up with.
I’ll leave you with this little bit of wisdom: Never, EVER underestimate American ingenuity, especially if they’re being forced into a corner.
I'd recommend a visit to David Gingery's Bookstore.
While they're busy being ingenious, they still have to eat.