It's food for a specific niche though. More broadly, the US government does have a strategic grain reserve, holding wheat, corn, sorghum, and rice. Or at least, there was one, until 2008 when food prices spiked and the grains were all sold off. The reserve, called the Bill Emerson Humanitarian Trust, continues to exist to this day, but only holds cash/securities and no longer holds grains/commodities.