I read an article recently–one of many–that was lamenting the loss of national unity felt immediately after 9/11. Given the numerous personal accounts I've read, it's pretty clear that 9/11 deeply affected Americans across the political spectrum–particularly the random subset of Americans who happened to be in the towers on that fateful day.
When the right complains about a loss of unity, they tend to blame moderates and liberals for basically veering off course, for failing to stay with the program. They fail to acknowledge that over the last 5 years, the program has shifted from a narrow, focused response to a specific event all the way to a grand desire to spread worldview, ideology and a socio-economic system to another part of the world.
This is key to understanding why we're not "all on board."
Immediately after 9/11, America WAS unified–and still is, I'd venture to say–in a desire to see the perpetrators of that horrific tragedy brought to justice. That means Osama Bin Laden. Many of us still look forward to his capture and trial, and for a few months after 9/11 it looked as if we were closing in on the top guy.
But then, the mission expanded–the fight to bring Bin Laden to justice became the "War on Terror," with its first stop in Iraq. We barely had time to accept that we'd lost Bin Laden at Tora Bora before we were talking up "Shock and Awe," and a VERY QUICK WAR, to rid the world of Saddam's WMD. And don't be confused or think that Tora Bora was unnoticed or has been forgotten among those on the left–a post about the failure to capture Bin Laden got 172 comments this week on liberal site DailyKos. We noticed, and we observed America's short attention span at work. Or was that George's?
Some of us recognized before 2000 that "W" might want to get back at Saddam for trying to kill his father, and suspected that if presented with an opportunity he might try to do so. Turns out, that was so much to the forefront of Bush's mind that he asked Rumsfeld–ON OUR NATIONAL DAY OF TRAGEDY, 9/11/01–to try to tie Saddam into the event, as well as Bin Laden who was already suspected.
So we're now three and a half years into a war that Rumsfeld dismissed as unpredictable, but estimated "It could last six days, six weeks. I doubt six months." Now we hear rumors–entirely believable, given this Administration's behavior–that Rumsfeld at one point threatened to fire the next person who tried to plan for securing Iraq post-war. This, mind you, for something many of us consider a diversion from the REAL threat–namely, Osama Bin Laden!
As the Iraq situation has become more and more depressing, the mission has now grown to be even more bloated and vague–to spread democracy to the Middle East. Many people don't believe our sons should be dying to "spread" our worldview, ideology and/or socio-economic system, or that Iraq had anything to do with 9/11, but many of these are people who DO believe chasing and capturing Bin Laden–who DID perpetrate 9/11–would have been worthwhile.
In conclusion, the problem boils down to the Bush/Cheney expansion of the mission from a response to 9/11 to the grand spread of freedom to the Middle East. Bush has tried to sell this as a way to combat the prevalence of terrorism, but no-one knows if it will work. Plus, many educated individuals–Wes Clark, to name just one–believe there are other strategies we could choose instead of bombing people into democracy–tightening our borders, examining cargo from ships, and playing nicer with our neighbors is one example.
So if Bush wanted to change the mission and maintain the sense of unity he had to begin with, he did a poor job of selling the bait-and-switch job.