According to Brendan O'Neill, the US is now justifying its continuing presence in Afghanistan as part of the "war on drugs"! Of course, it was the US invasion that kicked drug production into overdrive. And that invasion was justified by how bad the Taliban were, and, of course, the Taliban were there due to the previous US intervention!
It would be nice to live in the land of Cockaigne, where roasted squabs fly into the workers' mouths, and government interventions are not subject to the law of unintended consequences. But since we don't, you'd think people might eventually learn that.