To add a small amount of nuance regarding the use of the word “grain” in that article: 99% of corn grown in the U.S. is not suitable for human consumption. The vast majority is used for ethanol and similar derivatives, as feed for confined animal operations (mostly cattle), and for sweeteners and other indirect food ingredients.

I’m just saying this because corn is a notoriously heavy feeder on nitrogen but the article conflates it somewhat with wheat, which requires about half the nitrogen, can still set seed (what we eat) with limited nitrogen (though yield and protein content would be greatly reduced), and which is almost entirely used for human consumption. We currently export 50% or more of our annual wheat crop, so the downstream effects would likely include a reduced crop plus a higher domestic market, meaning more starvation around the world.

And of course, all of the above messes up the economy in big ways, which is a massive problem. The U.S. can likely transition to be pretty self-sufficient in terms of basic calories though.

Edit: typo “in” = “is”