True enough but still that is one region vs North East, Southern California etc as shown by your map as well. So Id still much rather be in a red state then blue state (which I am in) when (!) zombies plague breaks. Plus the Texas Triangle might be a megaregion but its also going to have many more guns so even megaregion vs megaregion its chances are higher. Not that it matters since Ive argued against military being able to react quickly enough to matter.
*edit* For anyone watching it right now...heh, totally awesome scene glad they followed that part of the book