Ilya Somin over at Volokh Conspiracy often blogs about how the average American is rationally ignorant of government. They don't know much about it, they don't particularly care what it does--and this is rational. It's not worth spending a lot of time voting, because your vote doesn't change much.
I cringe when I read stuff like that. Yet now that I am teaching State & Local Government again, it is clear that this accurately describes the 1/3 of the American adult population that never votes. Some of these are 20somethings, but even many of the adults in their 40s aren't clear on the difference between a state legislature and Congress. Why? They never much cared what government does, and so didn't pay attention.