There are plenty of Mexican illegal immigrants in Canada, probably helping with our huge pulse crops.
Anyway, there's no point in enhancing the productivity of U.S. domestic agriculture. It is incredibly productive and food is incredibly cheap at the wholesale level. If it becomes a bit more expensive at the wholesale level, I doubt that will shift the consumer price all that much. The people who would have more trouble affording food would also have higher mean income, since they would be more likely to be employed.
Anyway, there's no point in enhancing the productivity of U.S. domestic agriculture. It is incredibly productive and food is incredibly cheap at the wholesale level. If it becomes a bit more expensive at the wholesale level, I doubt that will shift the consumer price all that much. The people who would have more trouble affording food would also have higher mean income, since they would be more likely to be employed.