Calling the Shots
The viability of military action in Syria and the credibility of McCain aside, the President as Commander in Chief has supreme authority over the US military and requires no authorization to employ the armed forces at his command.
The balance of power does not lie in any illusion of Congressional authority or War Powers Resolution, but in the power of Congress to cut off funding.
Congressional power to “declare war” refers more to a total war effort of the nation as a whole and not to all military action. We see evidence of this all throughout US history. There’s been military conflicts initiated by Presidents and funded by Congress since the late 18th century, just 11 years after the ratification of the Constitution. See “The XYZ Affair and the Quasi-War with France, 1798-1800”.
This is all rather academic and does not make the prospect of war any more appealing, but I find it disconcerting when folks incorrectly invoke the Constitution selectively or ignorantly.