The atrocities in Afghanistan are being committed by NATO, not just the US. No nations in history has practiced the policy of 'kill them all and let God sort it out' more assiduously than the USA and Great Britain. Take fire from a village, call in an airstrike and wipe it out. That is the American Way of War. Of course the US would stop an investigation. Though were we wise we would welcome it. Since WW II our favorite 'clean' form of warfare, airpower, has been the single force most responsible for people opposing us. We have killed far too many noncombatants in Afghanistan and that is the single factor which has aided recruiting for the Taliban. You do not win their hearts and minds by killing their women and children.
from the article: UN Gaza report / Will U.S. now let Goldstone into Afghanistan?