If they're going to build a new Great Wall to keep the Mexicans out, the Wall should take a hard left and include Texas and Oklahoma, turn right to include Arkansas, curve upward to include Kentucky, continue upwards to include West Virginia (not so much "South", but run like a Southern state with bonus coal) and finish up somewhere in Virginia dependent upon, if by that time, the terrified residents offer George Allen and Oliver North as apologetic sacrifices to the remorseless and vengeful Wall.