The United States has anywhere between 1.5-5+ years of food supplies in grain storage alone, depending on the time of year. And that’s not counting anything in the fields. In addition, the paper you cited makes some very bad assumptions (no change in crops to account for different weather, no increase in land cultivated, not taking into account existing food stores after year 1) that make the conclusions effectively useless.
By sheer coincidence, I wrote an analysis of that exact paper earlier today.
https://www.lesswrong.com/posts/sJK6HN5vTPPnuuNgQ/that-one-apocalyptic-nuclear-famine-paper-is-bunk
https://www.lesswrong.com/posts/jnDibtfvWNHLucf4D/actually-all-nuclear-famine-papers-are-bunk
The United States has anywhere between 1.5-5+ years of food supplies in grain storage alone, depending on the time of year. And that’s not counting anything in the fields. In addition, the paper you cited makes some very bad assumptions (no change in crops to account for different weather, no increase in land cultivated, not taking into account existing food stores after year 1) that make the conclusions effectively useless.