That's not true. The overrepresented regions are basically the South and the West. The Midwest “flyover states” and Northeast are the most underrepresented areas.

And while the South is overrepresented, (Also, military recruitment isn't necessarily politically representative of the states it is drawn from; sure, the Deep South is overrepresented, but that's also a big part of the reason the Blacks are super-overrepresented in the military (making up nearly triple the share of the military as of the country at large.) And Southern Blacks politically don't look the same as “the South” more broadly.