I know you're probably using Michigan just as a foil, but Michigan is sort of a weird case. The land that's able to be farmed is being farmed very well. The problem is that north of a certain point the land is just not very arable[1] due to a number of factors including soil quality and growing season length.

[1]: https://project.geo.msu.edu/geogmich/ag_regions.html

Many of the crops grown in Arizona and southern California such as lettuce and spinach are grown there to supply the country during the winter season.

Michigan couldn't replace that during the winter. So it's more of an issue that we would have to decide to only eat vegetables seasonally. No green leafs in winter. Or build vast greenhouses I suppose.