Trump is simply acknowledging that the U.S. has no credibility when it comes to protecting the territorial integrity of nations anymore.
Yugoslavia broke itself up before anyone intervened.
Then it fell into very bloody wars. Again, before anyone intervened.
And then NATO intervened, as this mess was stinking up the neighborhood.
President Clinton let Osama bin Ladin pass, but bombed Serbia.
EU was interested in flexing some muscle power. Plus, there was Virtue Signaling to the Muslim Brotherhood (supposed to be the nation builders designate: Egypt, Libya, Syria) - that resulted in a flood of “refugees” across the Med and mid-East.