This is something I've seen a lot of people saying on the internets, that "Hillary would start world war 3 because she voted for Iraqi Freedom and pushed for action in Libya."
I'm not convinced she did those out of aggression, it's probably for the same reason she years ago parroted the lines supporting a ban on gay marriage, she wants to stay popular, she doesn't lead, she basically goes "Where are all those people going? I must lead them there," and that's why the DNC likes her, she'll do what they tell her to do.
That might mean we get the same semi legal and wholly illegal wars and alliances we've had since the cold war and after (if it can be truly said the cold war ended, I'm not that convinced it did actually, it simply dropped into low gear when Russia took a break from being an antagonist), but they and she won't push us into world war 3.
Trump on the other hand, has a long history of huge fuckups, doesn't think before speaking, and is likely to appease Russia, giving Putin the impression he can take a few NATO countries without consequence, I don't see temper tantrum being the cause because I doubt the people around him would allow that, but it will be through bad policy decisions based on the premise that Russia Today isn't talking complete shit.
Either way, I don't think US foreign policy will get any cleaner, whether Trump or the DNC win.
"This calls for a special blend of psychology and extreme violence."