Actually, the US is the #1 exporter of ag products in the world. We are 5% of the population and responsible for 15% of the global supply of ag products.
Grain, yes, much of it for animal feed. Most other edible foodstuffs, no. The dollar balance on HUMAN FOOD has been negative since 2000. I've been on this for a while:
Want a REAL source?
Here is a 100 pp paper on the topic prepared for the Millennium Round of the WTO by the Center for North American Studies.
Here is the PowerPoint slide presentation that goes with it.
We are a net agricultural exporter. We are a net FOOD importer. (You can't eat cotton, tobacco, catfish, animal feed, and soybean meal).