But the president's authority was further brazenly undermined when a few days later the Saudi rulers endorsed the dissenting US diplomats – while being received at the White House. 

Several things can be discerned here. For one, the US policy on Syria is reeling from failure. The objective of regime change – which has impelled the whole war in that country for the past five years – seems to be fading as an obtainable goal. Russia's military intervention beginning last October to stabilize the Syrian state put paid to that. Reports that Abu Bakr al-Baghdadi, the top commander of the so-called Islamic State (IS or Daesh), has been killed in a Syrian/Russian air strike in the group's eastern stronghold of Raqqa suggests that the foreign-backed terrorist insurgency is indeed facing final defeat. 

The US covert tactic of using a dual-track political process of supposed peace negotiations to allow for mercenary proxies to regroup has also come unstuck.