There's a free video up at Hulu called "Split: A divided America." It was interesting, although off point in many places. For example, they cite Thomas Jefferson edited a bible as evidence for his religosity. That was true, Jefferson wrote the Jefferson Bible. However, the Jefferson Bible was notable because it removed every single last supernatural reference from the Bible, leaving just the philosophy. Jefferson had beliefs far outside the norm of Christianity, and would be best described as a Deist.
I also don't think you can discuss the issue without thinking about in-group/out-group psychology.
Anyhow, I think the movie's worth a watch and think. Even if the production values aren't that great.