It's too tough for me to say. A lot of people will simply say we should mind our own business and we aren't supposed to be the "Big Brother" of the world but politically and economically speaking it would cost us greatly down the road to lose our status as "top dog" among other countries. There's a reason why we strive so hard to be The superpower in the world. It gives us leverage for all world affairs, including trade and other important negotiations. If we were to slip on the power scale, then our influence would as well. That is one of the biggest reasons why we usually don't "mind our own business".
I'm not saying that this isn't a moral issue as well, but it's really more political than some realize. Also there's the downside to being the top dog. We are also the top target. So we kind of need to be involved in other affairs in order to know, and more importantly control possible threats. If we just keep to ourselves, there's a chance we wont be able to prevent a terrorist power to rise in influence, which their influence could take over their country, which influence could then spread to other nations, which could lead to chaos and world war.
In a perfect world I would love to just let this one go and let everyone take care of their own issues. But unfortunately we are affected by what goes on in other countries whether we like it or not. George Washington for-warned that we should be wary of treaties and getting into foreign affairs, but then again, he never had to deal with nuclear threats that could wipe out the country in an instant. I say if we are going to do this, we do this as quickly and as definitively as possible. This isn't the same as the Bush era "weapons of mass destruction" thing. We seem to have a better sense of what/who our enemy is and what we need to do, so while I hate to get involved, I do see the potential risks of not doing and at least I'm more confident in this than the last incident
