And the USA might be in a good position to broker some kind of standoff between the Kurds and Turkey in some way. Demilitarised zone or something? After all, this is entirely an aggressive initiative by Erdogan, supposedly to eliminate the threat of Kurdish terrorism. Turkey is a NATO member. There would seem to be levers, for an administration to use, if they are keen to avoid further destabilisation of the area - and the return of Daesh.
First of all, the US has tried hard to broker something. And this has effectively stopped the Turkish attack for quite a long time. Initial plans were to start it immediately after the Afrin operation.
The Turks several times felt being tricked by the US, in particular, because the US continued to support the Kurds with weapons. The typical scenario - in the negotiations the US is promising something but does not do what is promised. I would not wonder that behind this are not even lies but power games between the various parts of the US forces involved - the State Department wants X, the Pentagon Y, and the CIA Z. And everybody does what he wants to do without caring about the others so that what the State Department signs in some contracts with foreign powers will be simply ignored by Pentagon/CIA.
What the US has done now has, in fact, stabilized the situation. Because it was clear that the actual front lines are not forever. It was a question of time when the Syrians would start to get rid of the US occupation. And they certainly would have had possibilities, once even the Afghans have them. In particular, because the Kurds themselves are on most of the East of Euphrates occupants of Arab territories too, and war between the Kurds and the Arab parts of SDF was a question of time, not if it will start.
Now, we have an agreement between the Kurds and the Syrian government which the US has prevented before. And the Syrian army will take all the Arab parts - there will not appear big problems, the Arabs are happy to get rid of Kurdish rule, and recognize that Assad is the winner of the civil war, and if there are no US bases behind him, they cannot be cheated to try to fight without a real chance to win. The Syrian army will care about the IS, and if the US leaves Al Tanf, this will become much easier, because this is actually the main IS base. All this reached without a war. The Kurds will be reduced to their own regions. The Turks control some areas in Syria where they can send the Syrian refugees to. What is the problem?