You are assuming that the USA is "going to war". Presidents don't go to war, countries do. Some of us don't considering punishing for the use of chemical weapons is "war". But if you want to insist it is "war", then since Obama has never spoken about principles but has spoken about "the red line", then it is about "the red line".
Since it is totally in the lap of Congress, it will be their decision. If the Republicans vote against it then it is clear they are weak on defense. If they vote for it, then the Republicans are evil war mongers.
The answer is.....Yes? He set himself up for the loss of face he's now enduring. And Politico's hate loss of face so you know how it'll play out ultimately..
'Course...it ain't helped that despite the pictures of bullet-holed, gassed, children showing up on all our evening TV's that the global political "Leadership" continues to obfuscate and dither over all of it. So when is rape, rape? And war crimes war crimes? It seems it ain't so clear to said "Leaders."
Welcome to the monkey house. Same as it ever is around here.