Intricacies:

Iowa also produces a lot of corn for ethanol (superfluously, but tell the Greens that!), using land, machinery and labor that could be used for corn for food. I don't know to what extent subsidies cause or reward underproduction for price controls, but they could factor in, and I guess more so in states so devoted to agriculture as the Midwest. Of course, also to mention is that no matter exactly how much Iowa produce is consumed in the USA, some is also exported. Therefore the whole picture is not only domestic.

Same would go for explicitly mentioned Kansas and roughly for the whole general area of the Midwest.

On the other hand, it is not healthy to only eat corn. So other products would still have to come from elsewhere: Texas, South American and Australian cattle, for example. And Quebecois potatoes. And Indian and Southeast Asian rice. And Cypriot olives. And Belgian chocolate and beer. And German wine. And Iranian dates - how can anyone live without Iranian dates??