The Obama administration has already declared war on Syria, even if it isn’t “official” yet.
Consider the facts, all of them acts of war:
The U.S. now recognizes a group of Syrian exiles to be the official government of Syria;
the U.S. is providing direct support for rebels attacking the government;
the U.S. has coordinated with NATO to place advanced missile systems — and 400 U.S. troops — on Syria’s border with Turkey;
Obama has drawn a “red line” that, if Syria crosses, would result in U.S. direct military intervention. If any other country made similar moves toward the U.S., there would be no question that war had been declared.