The following is not only true for the US food system:

The American food system rests on an unstable foundation of massive fossil fuel inputs. It must be reinvented in the face of declining fuel stocks. The new food system will use less energy, and the energy it uses will come from renewable sources. We can begin the transition to the new system immediately through a process of planned, graduated, rapid change. The unplanned alternative-reconstruction from scratch after collapse-would be chaotic and tragic.

via REPORT: The Food and Farming Transition | Post Carbon Institute.

A commentary on the report was published on Treehugger:

While the report clearly articulates the trouble confronting a food system that has developed an addition to cheap oil, it also intelligently details what the US can do to survive when the drug is withdrawn, as it soon will be.

The full report can be found here.