As far as comparing Mississippi with Alabama goes, an interesting trend is that Alabama swung 10.7 points more Republican but Mississippi only swung 2.8 points more Republican.
This was something I didn't understand as well.
After all in Jefferson County and Shelby County (ultra-GOP Birmingham suburbs), the gains were only about 6%. However, the gains were about 20% in the exurbs of St. Clair County, Blount County and Cullman County of Birmingham proper.
I think by looking at the map, it appears like most of the Bush gains came in the rural white poor areas of Northern Alabama and the area surrounding the Black Belt in Southern Alabama.
The gains in the black belt correspond more to national numbers, gains of 3-4% or so.