The main point from our international point of view is that in his campaign, Trump led to believe that USA would have put an hold on their long tradition of interventionism.
Yeah I was also surprised by this move (both because earlier Trump seemed he wants to concentrate more on internal matters, and because it seemed he didn't want to anger Putin in any way)... but in this case I was pleasantly surprised, at least for now. I don't know what if any hidden agenda there was with Trump, but I felt this action was The Right Thing To Do.
So I am not black and white about "US should (or shouldn't) play world police", it depends what is achieved by that. For instance, I was also pleasantly surprised when Obama killed Osama. Farewell to that piece of scum too, I am glad US killed him even if it meant they illegally invaded Pakistan in doing so. Maybe Pakistan shouldn't be harboring terrorists then.
Similarly, if tomorrow CIA assasinated Kim Jong-un (and anyone in his regimen that tries to fill his place as a dictator)... say what you will, I would be glad even if once again US acted as world police. Heck, if Putin fried his ass, I would congratulate him, and not say "Russia shouldn't meddle with international matters!". Yeah teah, North Korea is a "sovereign country" just like Syria, but sometimes something just has to be done. I am sure that in 50 years when people talk about the atrocities in former North Korea, everyone will be asking why no one did nothing in the early 2000s but just let the atrocities continue there. Hindsight and all that.
Maybe this is just my frustration with e.g. European leaders who achieve nothing and are total wussies. Chemical gas attack in Syria and Europe seems to be like "This is criminal to humanity, we object this strongly" and that's it. Or Erdogan saying this and that and the EU leaders are like "now now, that was not a very nice thing to say, you hurt our feelings by calling us nazis". Send the nukes already, dammit! (figuratively only, of course)