The US isn't dependent on imports to feed its citizens, in fact I'm sure that we're a net exporter several times over for most foods (but oh how I'll miss my kiwifruit). However, breakdown in distribution systems, until the government steps in and (hopefully) gets things moving again, could be scary for a while. Also we might have to make some decisions that politicians may not have the vision or courage to do, like "we're going to stop feeding all this grain to cows for a while, and we're all going to eat basic staples and very little meats, since meat is an inefficient use of plant protein, and we want to be sure we have enough to feed everyone." Anyway, just saying.