Douthat puts the United States' international obligations in context:
We would become part of the government of Libya, in a sense, if we engage our forces in that country’s civil war. And thus our obligations to Libyans would increase, and so would our share of the guilt if things turns out badly.
It isn’t that we have no obligations to Libyans now: As the dominant power in the globe, we have some responsibility for furthering peace and order just about everywhere on earth. But just as you have certain obligations to your brother or cousin’s or neighbor’s child, but a far greater responsibility for a child that you adopt, so a great power’s obligations increase when it assumes an active role in the politics of another country and so do the responsibilities it bears for any subsequent disasters. Which is, in turn, a good reason to be wary of taking on too many of those obligations in the first place.