That, while not the majority, a big chunk of the American population feel left out and left behind. While their tactics for dealing with that are often terrible, those in power might want to make some real effort toward addressing their concerns.
That truly caring, intelligent, and talented people have no interest in running for public office. As such, we are left with average to horrible choices in a two-party system that does not work.
That bigoted, racist, sexist, homophobic people exist in greater numbers than you would have imagined, if you live in a fairly moderate to progressive state (like I do).
That the US is simply too large, both geographically and population-wise to achieve any real unity, particularly given our focus on individuality.