I'm also kind of surprised by what looks like a majority of geographically large districts in New York, Michigan, Wisconsin, and Nevada being red.
The large central district in Nevada (the new 4th district) is dominated by the heavily black/Hispanic and generally economically deprived North Las Vegas. The northern district (the 2nd) is of course based in Reno. Obama's margins in those two cities were large enough to turn both of these huge districts red simply because the desert areas are just that unpopulated.
