Shelby TN 6%
Dallas TX 4.5%
Montgomery AL 4.5%
Harris TX 3.5% (wowzers!)
Jackson MS 3%
You have to be making some bad assumptions to get these numbers. There are precincts in most of these counties that are all but 100% white, and they don't vote 95% Republican. 80% Republican, sure, but not 95%. In Harris and Shelby (and maybe in Dallas?), there are even a few heavily white precincts that voted for Obama. 20-25% seems like the lowest possible white-for-Obama percent in urban counties (then down to more like 10% in some rural counties in the South).
Yea my math may off in some of these places , I was looking at the non-Hispanic white population in a given county and comparing it to Romney's vote total
Example:
Shelby County, Tennessee: White persons not Hispanic, 38.6%
Romney's percent in Shelby 36.55%
Clearly he got basically a very tiny amount votes from blacks in Shelby and very few from other minorities.
Virtually all his votes came from that 39% that were white-non-Hispanic.
Now Texas and other heavily Hispanic places are tough because it's hard to figure the turnout because of non-citizenship and Texas Hispanics are more conservative than others.
Another easy one:
Montgomery County AL
Non-Hispanic white 38.3%
Willard Mitt Romney 37.5%