The prospect is frightening. The political instability that a food crisis on a continent-wide scale could cause is really beyond our comprehension. As a species, we've never faced it before.
Expensive food is one thing when there are cheaper alternatives. When the cheap food is your only nutrient staple and you can't even afford to eat that, the situation becomes dangerous. Widespread violence is going to be the result.
Remember, that's one billion people. If even a fraction decide that they're going to gate-crash another part of the globe, we'll be severely overwhelmed and looking back with fondness when it was only the Mexicans we had to worry about.