That would be a serious mistake.
The situation in Iraq is stabilizing but it needs time and effort. Our enemies are pressing the matter hoping that we lose our nerve; leaving now would give them exactly what they want.
Leaving Iraq now would result in an actual, real civil war which would end with a totalitarian Islamic government worse than the one we went in there to depose.
The idea that Iraq is even remotely similar to Vietnam is, itself, ludicrous. The situations are not even remotely parallel; the only similarity is that the government we are trying to support now would collapse without our help, much the same way the South Vietnamese government needed our help in the 1970s.
In 1972 the South Vietnamese Army repulsed an invasion from North Vietnam--a major tanks-and-infantry type of invasion. That invasion had been repulsed with a US military loss-of-life around 300 KIA. Most of the casualties in that fight were taken by Vietnamese--North and South alike.
The dirty secret of the United States' "loss" in Vietnam is that we didn't actually lose anything. At the time of the fall of Saigon there were hardly any US troops in Vietnam at all; the Fall of Saigon in 1975 took place after--get this--
the Democrat-controlled Congress of the United States voted not to give military aid to the South Vietnamese.
You read that right. The Democrats voted against sending our nominal ally, South Vietnam, any serious aid--not even materiel such as ammunition. Without such basic necessities as bullets, the South Vietnamese Army was pretty much a pushover. The NKVD rolled over the SVA, and Americans had to flee Saigon via helicopter.
These days no one really talks about the critical role that the Democrat vote played in the resulting carnage--2,000,000 people were sent to labor camps, and 100,000 were liquidated--and Laos and Cambodia underwent Communist "revolution", leading to (among other things) the atrocities of Pol Pot and the Khmer Rouge.
The Democrat Party of the United States voted not to support an ally; and the result was that ally's destruction.
But what does Vietnam have to do with Iraq?
First off, the Democrats themselves keep comparing Iraq to Vietnam. Part of it is that they desperately want it to be the ten years from 1965-1975 again, when they were enjoying being in charge and socking Republicans in the face. The lowering of voting age to 18, rolling in all the votes of the college kids who didn't want to be drafted and who voted with their feelings rather than their intellects--the Democrats received a serious surge in their constituency from that. Besides, around then, black voters began to drift away from voting Republican (as many had since the days of Lincoln) and began voting Democrat even though Democrats had stood in the way of the Equal Rights Act.
If Iraq=Vietnam, it means they might be able to use the same tired anti-war template to rally young people to their side. Since the commencement of hostilities in Iraq, how many times have proposals come to the floor of the Senate and House to reinstate the draft? (Look it up. And look up what party the sponsors of the bill belong to. Hint: it doesn't begin with an R.)
If Vietnam was a disaster, then it was a Democrat disaster--a Democrat got us into it; a Democrat escalated it; and Democrats finally abandoned Vietnam in its hour of need, when all it really needed was ammunition and weaponry.
When America refused to support South Vietnam, its ally, the country it had supported against North Vietnam for almost a decade, it sent a signal to the rest of the world: "If you ally with the United States, it will only support you as long as it's convenient."
Rather close on the heels of this, then, came Iran, in the Carter years.
The Carter administration refused to support the Shah of Iran. US foreign policy had, until then, supported the Shah; although there were things about the government of Iran which the US found distasteful, he kept the country stable. But under Carter, that changed; and ultimately the Shah fell and was replaced with a different government...
...a government which was basically under the sway of our good old buddy, the Ayatollah Khomeini.
The fall of the Shah of Iran reinforced the "Vietnam" template: "Ally with the US at your own peril. They'll abandon you when you need them the most." The show of weakness culminated in the "student" seizure of the US Embassy in Tehran...and a hostage "crisis" that should have resulted in a US declaration of war against Iran, but which instead led to mealy-mouthed "negotiations" and a botched rescue attempt--all of which made the US look weak and pathetic at a time when it could ill afford either.
Vietnam and Iran in the 1970s are basically at the root of the entire problem we now face with Islamic totalitarianism. Those who would rule the world with the iron fist of Sha'ria were emboldened by the abandonment of Vietnam and the emasculation of the Shah. A US that would not even declare war after an act of war had been perpetrated against it was obviously a weak US, one that deserved destruction.
And so, 9/11/01, the culmination of literal decades of low-level terrorist attacks against US interests. And before October of 2001 had ended, Leftists began to castigate America, telling it that 9/11 had been America's fault.
In a way, the Left was right...but they did not tell the whole story. It was America's fault because of the actions of the American Left.
The Left did not and does not like it when America defends itself. The Left voted against funding a South Vietnam self-defense. The Left avoided going to war against Iran. When Reagan struck at Libya in the 1980s, the Left collectively wet itself, shrieking that the attack would only invite further retaliation. (The fact that no US interests were hit for years afterwards seems to have escaped their notice.) The attack on Iraq was similarly characterized; and the mass terror attacks which have been collectively labeled "insurgency" in Iraq are claimed to be the result of the US attacks on Iraq, even though most of the "insurgents" are Syrian and Iranian imports, not native Iraqis.
The insurgency has fueled the continuous "Iraq=Vietnam=Quagmire" drone, which itself is meant to flay the American people into a mindset which will allow a Democrat "de-funding" of the War on Terror.
No one in the Democrat party dares to vote against funding the war in Iraq right now. The war is portrayed as "unpopular" now, but they know well the feelings of the American people. They will spend hours denouncing it, but when the question is called most will stammer something about "the troops" and vote for continued funding, pretending to hold their noses.
When the American people demanded action in the wake of 9/11, Democrats did not dare vote against it. The same Democrats who voted for hostilities in Iraq now wish us to walk away from it; seeing no political advantage in continued war against terrorists, now that the atrocities of 9/11/01 are a distant political memory, they wish the military to once again go back to being a distateful necessity rather than a front-and-center implement of foreign policy.
Ultimately the only way that Iraq can be like Vietnam is if the Democrats "de-fund" our efforts there, the way they de-funded Vietnam in 1975. The results would be equally horrific and just as much the fault of Democrats.