Cheap labor and very lax environmental laws make them very competitive in manufacturing.

There isn't that much labor involved in modern North American hog production anymore and the environmental costs are offset by using the manure for fertilizer.

The only part of the Corn/bean > pig > pork on the plate cycle where they'd have a real advantage with cheap labor and lax environmental laws is in packing/processing side.   But US packing plants are very very efficient also.