No matter what motivates you—realpolitik, humanitarianism, nationalism, whatever—interventionism doesn't make sense if it doesn't work. And the lesson of the past decade, at the very least, is that interventionism is really, really hard to do well, even if your bar for "well" is really, really low.
The first question for any kind of action in any sphere of human behavior is, will it work? If the answer is yes, then you can move on to arguments about when, whether, and what kind of action might be appropriate. But if the answer is no, all those arguments are moot. In the case of U.S. military interventions, the answer might not quite be an unqualified no, but it sure seems to be pretty damn close. This makes the rest of the argument futile.This is related to commenter Charles's recent point: arguments for intervention always gravitate towards abstraction, because actual recent history is so resolutely discouraging towards intervening.
I am never surprised that our past failed interventions haven't turned people, particularly liberals, into committed non-interventionists. I am always surprised that our past failed interventions haven't inculcated skepticism and prudence. Peter Beinart wrote a famous reevaluation of Iraq:
It begins with a painful realization about the United States: We can’t be the country those Iraqis wanted us to be. We lack the wisdom and the virtue to remake the world through preventive war. That’s why a liberal international order, like a liberal domestic one, restrains the use of force—because it assumes that no nation is governed by angels, including our own. And it's why liberals must be anti-utopian, because the United States cannot be a benign power and a messianic one at the same time.I have not observed any injections of wisdom and virtue into the American character since then. We are still not that country, not the country which ends suffering thanks to its righteousness and its strength. Recent history suggests that we are in fact still that country that causes suffering thanks to its clumsy and oblivious nature. And that fact is the one I expect people to hold onto, not yet seven years after Beinart wrote this essay. The cruel joke of Beinart and his piece, of course, is that he could only arrive at it after he had said despicable things about those who had opposed the war, and only after untold thousands were dead. That's always the way of things: they rediscover the nature of American power only after the bodies are buried. The unintended consequences reverberate for decades.
I see people latching onto Mali-- yet another good war for people desperate to find them-- and I wonder how much time they spend thinking about just how wrong things can go, just how little it matters that their hearts are pure. They will find themselves surprised to find that they live in the same old fallen world, home to the same old United States.