The US is claiming that Russia is “propping up” the regime of Bashar-al-Assad in Syria. This is why they won’t coordinate their anti-ISIS efforts with Russia. 
The US – as they have from the very start of civil unrest in Syria – supported the demands of an opposition for the removal of Assad as a pre-condition for talks.
Yet Assad has widespread popular support in Syria.  He would almost certainly win a Presidential election. This is why the US has to pre-insist that he goes before any political solution is found.
As always the US is gerrymandering a regime change. As always ‘democracy’ means what the US thinks is good for its interests. It never means actual democracy. Look at Algeria in 1991. An Islamic grouping was poised to win elections. The military intervened. The elections were cancelled. And 7 years of a bloody civil conflict followed. No voice from the West then about ‘democracy’. The same more recently in Egypt where the ‘Arab Spring’ led to the Muslim Brotherhood being elected. They were deposed within a year by the army. The US announced that they didn’t support coups and they stopped some of their aid to the Egyptian army. As to be expected though this has been silently being re-started.  At any events, and again, no calls in support of democracy in Egypt.
The position of the US is naked: they want what they want (the departure of Assad and thus the breakdown of the Iran-Syria-Hezbollah axis). International law has nothing to do with it. The US is a rogue state. The only reason they aren’t a pariah state is because of their economic and military power.
It is a pity that