Potatoes became an insurance against the all too common disaster of war. The disadvantage of depending on potatoes as a major food source is that they do not last in storage as long as grain does. Carryover from one year to another is impossible. Consequently, populations depending solely on the potato risk disaster in case of crop failure. Corn and most other American crops had a smaller advantage than did the potato in Northern Europe.
Corn requires longer and warmer summers then the potato.
Corn is a grain that had to be stored in barns so it was not the same kind of disaster insurance that the potato was further North. Moreover, corn lacks certain essential amino acids. A diet exclusively of corn will bring on a crippling disease called pellagra. However, corn had a couple of advantages other than increased caloric output per acre. Namely, landlords and city folk didn't want anything to do with it.