There is no right answer here. I don't get why people are freaking out so much.
The right answer was to not escalate this.
Assad already did that by gassing his own people.
We are NOT the world police. We shouldn't be escalating international strife unilaterally like this. There wasn't even debate in Congress.
We can't be world policemen, and expect to solve every problem in the world, or even get involved in everything in the world. But when something reaches a certain magnitude with an immediate crisis, we need to do something.
When it became clear years ago that tens of thousands (even without WMDs) were dying in Syria, we needed to do something. And with hindsight, it might have also prevented ISIS from filling the vacuum, the international refugee crisis stemming from Syria, and the xenophobic/isolationist/anti-Muslim backlash that has rushed the Nationalist Right to power across Europe and the United States.
One of Obama's biggest mistakes.