[philwelch]

> Is it because the US isn't willing to go total war and massacre civilians until they give up Mongolian style or what?

Home field advantage and the ability to use guerrilla tactics have always been a tremendous advantage, and often it's enough to make it prohibitively expensive to conquer or subjugate a given population rather than just leaving them alone. This, combined with terrain, is what makes Afghanistan in particular so defensible in parts.

For the US in particular, there are also levels of brutality that we're not willing to resort to, which only helps to tip the scale towards "too expensive to be worth it". Russia had much better luck with their counterinsurgency efforts in Chechnya, but then again, Russia is willing to resort to measures that the US is not. Though even then, the desire to maintain Russian territorial integrity probably justified higher costs than the desire, in the 70's and 80's, to maintain communist domination of Afghanistan.