Go watch "Jesus Camp".
Having not watched Jesus Camp, but knowing roughly what it's about, I think that's a big oversimplification.
I'll give the red areas a shot.
I grew up in Central Indiana (Indy suburbs). Plenty of people go to church. Plenty don't. I don't know too many people that I'd call religious zealots. Now, in the county where I lived, there was a fair amount of money, so I think Republican notions of lower taxes tend to appeal to them. And why not? Your best estimate of how things are going is your own life. Life was good, there, Republicans were always in charge, so there's a lot of party loyalty.
And I think that general rule of thumb will apply to a lot of suburban areas, where you have a large middle class population. And the middle class, especially, is hostile toward a lot of policies that are traditionally tied to Democrats. Take welfare and affirmative action, for instance. The middle class is the group of people who exemplify the American dream, in that they worked hard, and were rewarded for it, and I think they dislike policies like welfare and affirmative action because they're helping others to get what they did, with what they perceive as less effort.
Finally, if you live in the suburbs, you're close enough to a decent sized city to know it's problems. Crime, violence, drugs, corruption...and who runs cities? Democrats! Why would a suburban want to elect Dems, when the places they're in charge of all seem to have enormous problems?
OK...that's the 'burbs, but rural areas are vastly different. First, it's more of a cultural and less of an economic loyalty to the GOP. While suburbans care about taxes, rural voters care more about the social conservative issues, like abortion, religion, and so forth. You'll find a lot more "Jesus Camp" influence in rural areas.
Of course, these are all generalizations...averages rather than overwhelming norms.
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