Yes and no. Under NAFTA Mexico cut farm price supports, while the U.S. kept them (or, kept them under different names -- corporate tax breaks, fuel subsidies for farmers, export credits, etc.) And, U.S. farms are corporate businesses (Old McDonald works for Conagra or ADM or some other faceless big company, not for himself) while Mexican farms were still mom-n-pop enterprises.
Mexican farmers couldn't compete and left (often for the U.S., to work for Old McDonald, who's working for...) meaning there are less corn producers in Mexico to start with.
With the end of restrictions on agricultural imports to Mexico ending this year, it's gonna get even hairier.
So, yeah... in a roundabout way, it is NAFTA's "fault".