In the Vietnam War, the U.S. faced a sovereign nation — North Vietnam — backed by both the Soviet Union and the People’s Republic of China. Our adversary in that conflict had a capital, a country, and a government. The goal of the war was ostensibly to prevent the takeover of the South by the North.
That’s not the situation in Iraq. There’s no single enemy: what our forces face is a mélange of groups, each of which has its own agenda, all of which are opposed to the U.S. occupation. There’s no capital to bomb, as we bombed Hanoi. The largest external supporter of the opposition is Iran, which doesn’t have the status or resources of the Soviet Union or China in the ’60s. There’s no government opposing us. Insurgents aren’t sneaking through the DMZ or along the Ho Chi Minh Trail to get to where they’re launching attacks, they already live there.
A more correct comparison is Palestine. Apart from the fact that our Palestine is on the other side of the world and not next door, the situation in Iraq looks a lot more like the Occupied Territories than Indochina. Military force in the hands of a foreign power? Check. Impotent local governmental authority? Check. Thousands of detainees held without charge plus occasional torture? Check. Multiple militia groups executing attacks on occupiers and carving out some local civic control? Check. Occupier responses to attacks that have a tendency to kill civilians in the process? Check.