What if the US leaves NATO ?
US is NATO. They can only disband it. Unless you believe in fairy tale that EU is some kind of military superpower
As for Trump waging wars, if he's going to do it Republican style I don't give a fuck. Rape Middle East, give everything to Jews to subjugate it, fuck the whole Northern Africa, I just dgaf. Besides Turks decided their future when they supported democratically elected government aka Erdogan. Whatever is coming for them, they fully earned it themselves. Our job is to make sure Europe doesn't get involved in more of that shit.
So yeah, I prefer Trump if he's going to wage wars in Middle East more than Clinton who could restart the Balkan wars. Because I'm fucking biased, sue me.
Edit: What I think that Trump will try to do? He'll try to copy success of China, start bunch of projects in America, bring even more people but who will have to work, not sit on welfare whole day. After all, that is how America became great. Brought Chinese workers or slaves to construct railroad for them. Great nations are built on hard work, not made on false promises which is only thing modern liberals seem to be capable of delivering.
About European politics, all those politicians who shat on Donald Trump, their days are numbered and that has nothing to do with Trump. By stopping him to get elected they tried to buy themselves time. There is no time left for the likes of Merkel, they are done.