Putin and Assad are scum, Assad is partners with Iran who definitely killed US soldiers in Iraq but some folks speak well of Assad. Syria invaded a Christian nation in Lebanon so I wouldn’t put much in the myth that Assad protects Christians.
If you were a foreign nation (especially a powerful one), would you sit around and watch the U.S. project its influence over the entire Middle Eastern world....just saying. Imperialism (even if it claims to be done for “world peace”) is going to draw a reaction among other nations. They aren’t stupid.