Putin does not desire a conflict with the US. I think he is concerned about being in the middle between US and Iran.
He basically says he does not want in that fight.
So, Here we are.
I think Assad wants to take Russia’s advice but is deeply indebted to Iran.
Both Assad and Iran saw what we did helping the Kurds. It should have been enough to dampen their enthusiasm for a conflict with the US military. But in Iran and Turkey’s case, I doubt they ‘got it’.
Assad will see that he alone cannot un-invite Iran from Syria.
Iran full well knows our capability - but have not be shy about confronting us, from the hostages in our embassy in 1979’ the Beirut Marine barracks bombing in 1983, though the thousands of IEDs in Iraq.
Turkey under Erdogan is a new problem for us and the region, but Iran is a well known opponent. They have come to Syria to establish de-facto rule, like they did with Hizbollah in Lebanon.