2) We are extremely vulnerable to sudden extinction from a variety of sources, yet it's on almost no one's radar.
3) That conspiracy-theory nuts are even a tiny bit right.
4) The growing reach and intrusion of the Federal government, most especially the unnerving growth of power in the Executive branch. Things are OK for the moment, but all that power is just accruing, and waiting for a nutbag to slip into office. Remember, Hitler was elected.
5) The appalling growth in pseudo-scientific beliefs, unto hostility towards the hard-won knowledge and methods of human scientific endeavor. Science delivers the goods. Woo merely picks your pocket.
6) Disturbing degradation in political and interpersonal communications among Americans. Perhaps it actually has always been this way, but both the scale and vehemence, due to technology, is very worrying.
7) The Earth's climate is not a stable thing. It has changed, and it's undeniable. What shivers me is the sheer unpredictability of it all...no one really knows...it could be far worse than our worst guesses. Then again, might not be much of anything.