I would argue that the American people evolve in a less that ideal environment for constructive argumentation due to the biparty politics. It nearly seems by construction that if an issue is endorsed by a party, then the other must be against it. For the untrained partisan of party A, every partisans of party B disagrees on every issue by default. I can see why it becomes difficult to stay rational.

Obviously, some people are willing to meet and discuss constructively, but that requires additional efforts to think outside this biparty mold.