Bigger issue is that you'd have to get rid of the warlords and cartels in various areas. It's not that there isn't enough food, it's that people are keeping it from them.
The last time i checked Pheonix is in a desert. They irrigate, they ship food, they survive just fine. I don't disagree that it's stupid to live in a place that shouldn't be inhabited (looking at you sub sea level New Orleans) but hey, some people like it there, just be prepared to pay the premium.