> (the odd thing is that there is little dirigisme for healthy foods like broccoli and spinach but a lot for mass carbohydrates such as corn, sugar,...)

Mass carbs are how you feed people in the kind of emergency that might make having a strong domestic food supply extremely nice. People can always backyard-garden some greens. If you've got enough corn, wheat, rice, and/or potatoes (maybe), the rest will sort itself out. If you're lacking in those, people are gonna die.