More troubling than Christians wrestling with the issue of response is the distinctly European reaction that questions whether the act of the U.S. killing Osama bin Laden was itself justified. Thankfully my fellow Americans, even those on the left, don't seem to think this is even an issue worth discussing (though I imagine if it was one George W. Bush who did the killing rather than Obama, the question would quickly transform from a non-issue to a hotly contested issue).
In any case, I'm currently working my way through David Bentley Hart's Beauty of the Infinite. The vast majority of that text has little direct application to the issue at hand, but in the section I just read Hart does discuss how Christians should view their roles as civic beings, given the revolutionary reality of the resurrected Christ. He argues that Christians can't be entirely complicit with the powers of the world as Christ's kingdom is one that must ultimately, not only transcend those powers, but displace them. Having argued this, he goes on to caution against the other extreme:
There is small room in theology for that passive collaboration with evil that often only flatters itself with the name "pacifism". ... The self-adoring inaction of those who would meet the reality of, say, black smoke billowing from the chimneys of death camps with songs of protest is simply violence by other means, and does not speak of God's kingdom, and does not grant its practitioners the privilege of viewing themselves as more faithful members of Christ's body than those who struggle against evil in the world of flesh and blood where evil works.