The United States does not have food reserves (other than grain stored in grain elevators, which grain Tome implied Libland would instead be importing just-in-time). Here is what the United States has to look forward to in a national disaster:

http://www.google.com/search?q=you+will+survive+nuclear

You are a survivor. Doomsday has occurred and you are a survivor. While you are waiting for the spouse and kids to get home maybe you should do something practical. Like go down to the supermarket and lay in a bit of an extra stock.

You may notice that the little corner store has closed. If he has believed the rumor, he wants to save his stock. And besides, your money may not be worth anything tomorrow. You thought you had seen rapid inflation before but this is like from zero to a million in sixty seconds.

At the supermarket, if you are early enough, you will find pandemonium. If not, you will find practically nothing. Maybe a large bag of dog food (take it) and some cans of floor wax (forget it). The rest of the stuff was all in those carts that you met come flying up the walk as you came running down.

There won't be any girls at the cash registers, (they have done their shopping and gone). Besides, the cash registers aren't working anyhow, with no power. It may have taken the hired manager a little longer to figure out that he should grab what he can and head home to his family, but he has probably gone now. The only cops you will see are the one's grabbing stuff themselves.

Perhaps you ought to go to Wikipedia and look up the difference between Libertarianism and Anarchy?

How does a Libertarian system decide which roles (like researching the intentions of foreign states, and defending against them) a government should play, and which (like presumably researching the weather, and defending against natural disasters) it shouldn't?