Barack Obama believed in the Pax Americana, but, after the experience of the Iraq War, he wanted to do it on the cheap. Like the lawyer that he is, he preferred to solve problems in the fastest, least risky, and least expensive way possible. And so, he developed a style of building and assisting coalitions that came to be called (not completely accurately) “leading from behind.”
The results were mixed. He succeeded in negotiating the TPP and the Iran nuclear deal, but Trump is in the process of destroying both of them. The “pivot to Asia” may have moderated, but did not stop, Chinese aggression in the South China Sea. In Syria, one can reasonably doubt, based on precedent, that an approach similar to Iraq (direct military intervention) or Libya (extensive support for local surrogates) would have led to a better result, but we do know for sure that what actually occurred had seriously negative impacts on the US, Europe, and the Syrians themselves.
In contrast to Obama’s cool rationality, we are now in an era in which brute force and bluster are valued over alliances, diplomacy, and rules-based systems. The Pax Americana itself is under threat, both at home and abroad. How long will this phase continue? More on that later.