There are other reasons to be uneasy about trusting other countries to supply our food. Some have lax standards of quality and safety - look at the recent pet food kerfuffle, which was caused by wheat gluten from China containing nasty chemicals.

Also, do we want other countries to have that kind of hold over us? What if a new leader gets PO'd with the US and decides to withhold food supplies? We'd be idiotic to put ourselves in that kind of position, and yet I'm afraid that's exactly what we're doing, in the name of cheap convenience (i.e. short-sightedness).