My initial thoughts after this dark day:
1) Global warming is the biggest problem right there. I am not a yank, so they can decide to kill themselves with guns for all I care if they want so, and become more bigoted than ever, but this will affect the entire world. All the projection put a rise of temperatures by 4C degree by the end of the century, even if we considerably lower the amount of carbon. Now the second biggest emitter of carbon dioxide has as a president a global warming denier.
2) A new economical crisis, but I think this was inevitable in either case. In fact, I wouldn't be surprised if it gets better by having Trump as president, just because of his sheer unpredictability, while Hillary on the other side would have just continued the status quo.
3) Obama's hard work will be erased from history. Obamacare is dead, no background checks to get guns, etc etc. Anyway, just Americans will suffer the consequences here.
4) An extremely conservative supreme court. Again, Americans' lose.
5) I actually think that Trump will be less hawkish than Hillary, the relations with Russia will improve, as will be those with China. NATO will be interesting, but European states need to put more money on it anyway, and Trump will ensure that. His stance on Israel-Palestine conflict will be far more pro-Israel than it was Obama's, but I would have expected the same to happen also with Hillary.
6) The end of Paul Ryan?! I thought that he will be the next president after Hillary, now he will likely be destroyed.
7) There won't be a Mexican wall, neither Muslims won't be denied to enter US.
To conclude, the biggest problem is (1), and it is a very big problem, by far the biggest reason I wanted Clinton to win. I don't think that much will change on (2) and (7), I don't care at all for (6), and don't care that much for (3) and (4). I think that (5) is actually positive.
It won't be as bad as we think it will be, but still cannot help but think that humanity is doomed when it comes to global warming, and both US and China going almost entirely green energy was the only hope. Now, that is not going to happen (if it ever was).