You're confusing the Syria civil war/revolution with the use of chemical weapons. Two totally separate things. The U.S. made a decision not to intervene in the civil war. That has not changed. It is solely the use of chemical weapons, and their being against international war, that is the issue. That they were used during a civil war is irrelevant.
Obama isn't dithering, IMO. He's weighing the options and giving careful consideration to what we should do. This is what I want. I don't want a leader who does knee jerk reactions or succumbs easily to pressure from other countries or the Sec of State. Obama has a good track record in making thoughtful foreign policy decisions. If only GWB had given more thoughtful consideration to going into Iraq and not succumbed to the pressure from Rumsfeld and Cheney.