Steve Chapman (generally a libertarian conservative) argues that the nightmare scenario of the Taliban taking over Pakistan and gaining access to Pakistan’s nuclear arsenal is not very likely, and that our effort there could be counterproductive. I’m in no position to know for sure, but it seems like he at least raises some valid questions. Of course, the risk of underestimating the threat is important to consider as well.
I wonder if our global foreign policy is in some ways self-perpetuating. As a powerful nation, we (and much of the rest of the world) see ourselves as able and often obligated to aid in crisis situations and see threats to our security in far-off places. But those missions can’t be isolated from their surroundings, and we find ourselves, for example, worried about militants on the lawless Afghanistan-Pakistan frontier or the support of Iraqi insurgents by the Iranian and Syrian governments.
A British classicist and historian once said that “We seem, as it were, to have conquered and peopled half the world in a fit of absence of mind.” Britain didn’t always set out to conquer and rule new territories, but rather absorbed some of them after the actions of private citizens or companies. Rome always claimed to be acting in self-defense as it gained its Mediterranean empire; I don’t think that there was an overarching plan to conquer much of the known world. I think some of the same mechanisms are at work in expanding American power. (For the quote and comparison of Roman and American expansion, see this BBC article.)
I don’t claim that this is all original thought, but I think that the parallels are valid.