My understanding about the problem with the diet of "the current poor population of North America" is not so much that they don't eat enough plant food, but that they eat all kinds of over-processed food, full of saturated fats, sugars and salt, and that any kind of food they get, meat or plant-based is of poor quality. Removing meat from that diet, even the poor quality meats they can afford right now, sounds like it would hurt their diet even more, not improve it.