So, with out a huge history lesson--why did we HAVE go to war in 1941? Because Japan had the capability of owning the Pacific and conducting attacks on the lower 48. We went to war for many othr reasons but we had to go to war because of the awesome capability of the Japanese Empire.
Now, how long did we have to fight the war? We had to fight the war until that capability was destroyed. We chose to fight longer and I think that that was as good a choice as any. What about Germany? Germany was never a threat to the US, but certainly they would have been if the had been allowed to concur Europe.
Okay, no long history lesson--so, fast forward to Iraq--We did not have to go to war with Iraq in March of 2003--we chose to. Now, really bad planning and assumptions aside, it is 2005 and the statement made by the Chairman is "Defeating the Iraqi insurgency is as important to the United States as winning World War II was 60 years ago" (I had gross generalities) I would have to say no--the general is wrong.
Okay, lets say that Britain loses the Battle of Britian in Oct 1940 and the British Air Force is wiped out. Hitler doesn't invade Russia in the summer of 1941. And the United States loses the Battle of Midway in 1942 (assuming events stayed the same which they wouldn't have as the US would have entered the war to save Britain) So, by 1943 The axis powers are in control of the European Continent, Northern Africa and the middle east. The axis is dealing with a huge resistance movement but it has at least physical control. Russia is not comfortable but is more interested in dealing than fighting. Japan controls the Pacific, to include Hawaii--can attack our west coast at will and is easily able to handle the Chinese since the US can support them (Chinese). America must isolate herself in self protective mode move industry inland fortify the West Coast, build a huge east coast fleet and hope the European insurgency keeps the Germans occupied.
If we fail to defeat the insurgency in Iraq, and abandon the country before it is able to stand on its own--and then we anticipate its collapse into civil war and extreme fundamentalism and we learn from our mistakes in 1980s Afghanistan, we can apply assets to reisolate Iraq, Rebuild Afghanistan, and basically be back to 2002 in a few years. Yes, there will be economic problems a a handfull of folks still out to get us, but I don't see the same degree of danger/risk to the viability of the United States that would have existed if WWII was lost ---I mean, I don't think it will be good, and at this point I would rather do what it takes to win--manymore active duty troops, a lot more effort, a lot more aid (I am groaning too)--but a loss is not catastrophic.