We Europeans should be careful about the mote in the US's eye. -----sapere aude
Another problem is that America is not fighting a clearly ideological entity. In Vietnam, the enemies were Communists. Or so the narrative goes. Currently the enemy is Al Qaida, Baathists, Islamofascists, sometimes Sunnis, sometimes Shi'ites, 'rogue states', etcetera. A lot of these are ethnic and religious categories. This may lead to a longer memory.
On the ground, Vietnam was still worse than Iraq. But there was no official endorsement of torture in Vietnam, which also changes the story of the war. And there are plenty of opportunities for Iraq to escalate even further, unfortunately.