The US has a lot less to gain from diving headfirst into Syria besides that military base they have to get that sweet, sweet oil now that the SAA is no more. I firmly believe he US trying to oust Assad was always more about curbing Iranian and Russian influence in the Middle East than increasing the already high US influence there. Sure, Washington would love it if their puppet in the FSA somehow manages to firmly take power, but the primary goal was to have Assad get a Ghedaffi or have him leave Syria with his tail between his legs.