Maybe so, but if we want to play this arbitrary blue vs. red game, then many of the red states have some of the biggest, sprawling metropolitan areas. Dallas and Fort Worth are pretty much one big city now. I also can't picture anything surviving in the Texas Triangle. When Houston, Dallas-Fort Worth, and San Antonio get overrun, every small town inside that triangle would get wiped out as well. If I may, here is a map of the fastest-developing urban areas.
As you can see, the Texas Triangle is just one example. Arizona, from Flagstaff on down to Tucson, is becoming more urbanized as those cities link up. From up in Fort Collins, CO down to Albuquerque, NM, one highway is pretty much a belt of cities that also includes Denver, Colorado Springs, and Santa Fe. In the panic that is guaranteed to accompany the first zombie outbreaks, that highway will be clogged with cars and refugees... and the zombies will eat their way along the entire length of it. It looks like every region except for Alaska, Hawaii, and some of the mountain states would be royally screwed.