Yes this Vietnam-Iraq blogging is going to get tiresome but so are its proponents. Here we have Max Boot in the Wall Street Journal (subs. req'd; alt. free link) assuring George Bush that his only mistake was in not more fully embracing the analogy. Two things. First, Boot answers the question of what the US could have done to "win" in Vietnam --
By 1972 most of the south was judged secure and the South Vietnamese armed forces were able to throw back the Easter Offensive with help from lots of American aircraft but few American soldiers. If the U.S. had continued to support Saigon with a small troop presence and substantial supplies, there is every reason to believe that South Vietnam could have survived.
By "lots of American aircraft" and "substantial supplies" he means: bombing Vietnam to smithereens. That was the strategy. Of course it works in that you kill "bad guys" but you completely alienate the civilian population. That's why air force plays so little role in modern counterinsurgency strategy -- strategy that Boot presumably supports in the Iraq context. Indeed, Boot subtitles this part of his argument "The danger of winning militarily and losing politically" -- a distinction that does not exist in the Petraeus strategy for Iraq. There's no military victory without political progress.
Then, of the American "defeat" in Vietnam --
whose ripples spread around the world. In the late 1970s, America's enemies seized power in countries from Mozambique to Iran to Nicaragua. American hostages were seized aboard the SS Mayaguez (off Cambodia) and in Tehran. The Red Army invaded Afghanistan.
Which is what happens when you try to relate diverse events to a single cause. There was other stuff going on in the 1970s. The US backed Shah was getting increasingly repressive, cooking up Shia fundamentalism. Portugal pulled the plug on its African colonies and let the locals duke it out for control. The Somozas kept the earthquake relief money. And that Red Army invasion of Afghanistan worked out real well for them. Overall, it's a dreadful analogy for a dreadful war.