> Assad is trying to hold on to legitimate power where the US is attempt to purge Syria of his government using terrorists relabeled freedom fighters who have destabilized the entire country.

I think you are widely overestimating both the US involvement and its degree of control over the actors it has links to. I'd be surprised if the main sponsors of the various anti-Assad factions (Saudi Arabia and Qatar) had anything like firm control of the factions they are funding.