Later on Wednesday, George Bush is going to give a speech (link) to the Veterans of Foreign Wars national convention in Kansas City Missouri comparing Iraq to Vietnam and in particular the events that followed US withdrawal from Vietnam with a claim for what would follow with a withdrawal from Iraq.
Audience members and/or the press corps will presumably be ready with the following points --
US engagement in Vietnam was motivated by a theory of global retreat if it wasn't there, specifically that Communism would take over the region and the world. That didn't happen. The entire region is now de facto capitalist.
US withdrawal was opposed on the grounds that Vietnam would implode if it left. It didn't. Bush himself went on a harmonious visit there last year.
There was genocide in Cambodia following the US departure from Vietnam. But this was a consequence of military strategies pursued by the US while it was still fighting the Vietnam war, which weakened the government of Cambodia. Had the US gotten out sooner, or never taken the baton from the French in the first place, it's hard to argue that the Khmer Rouge would still have happened.
And, by the way, the US supported the Khmer Rouge and punished Vietnam for getting rid of them.
August shouldn't be an opportunity for bogus historical analogies to get a free pass.
UPDATE: Based on the White House Fact (sic) Sheet for the speech, it will also argue that Vietnam war opponents enabled al Qaeda --
Some Argue That Our Withdrawal From Vietnam Carried No Price To American Credibility – But The Terrorists See Things Differently. In an interview with a Pakistani paper after the 9/11 attacks, Bin Laden declared that "the American people had risen against their government's war in Vietnam. They must do the same today."
The speech is also oblivious to the USSR's role as an ally in World War II.