That would require taking out air defenses and Syrian aircraft.
And Russia would have to withdraw its aircraft of possibly get them destroyed.
Bring NATO in on this, Egypt, Saudi Arabia, Iraq, as well NATO member Turkey, and Russia has a big problem defending Assad.
Also I am sure Australia would join with NATO and Canada.
Start an air campaign with a strict warning to Russia, and Russians might get their tail ends kicked.
There are now former Eastern Bloc countries that are part of NATO (Poland and company).
We just need to arm Japan to cover that side of the world...
Our biggest problem would be keeping Israel out of the fight.
But then we could always play Good Cop/Bad Cop with them: "We told you Israel to stay out it. You were not supposed to shoot down those 100 Syrian jets and helicopters."
You’re a faithful friend of both ISIS and Al Qaeda.