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".
I see. Then the eventual solution will be for Mexico to abandon the mom-n-pop model. There seems to be a lot of nostalgia (I'm not talking about you, but in general) for the small family farm. The mom-n-pop type of farm. And there's a lot of animosity for what many call "corporate farms". I have a completely different view on that. I think that huge farm operations are wonderful. They've brought the price of food down, it's more plentiful than ever, and there's more variety than ever.
There are nations in which this corporate farming hasn't taken hold but they're third world nations, and many of them are starving.