We are talking about a full go-out, regime-change, war, based on FALSE premise/accusation. You can always spin it as a result of shaky intern, noble cause, or strategic long-term goal, but it was a major blow to the credibility of US, as a country. It hurts the economy and confidence in the government. It escalates the hostility between two-parties. Those are what hurt US the most in the long haul.
It was a war led by an intention - that's the most dangerous part. Bush wanted this war, so non-conclusive or even just remotely related intern was shaped to serve the goal. There is nothing democratic about it, and that's where the real threat lies in. As I argued with Americans, Patriot Act was an act of diminishing in value. That's how police state gets started.
After 911, most countries with influences (except for China) had their front pages of major newspapers in black, "We are New Yorkers". Afghanistan War was a justified revenge, had most countries behind it. Iraq War OTOH, was not even supported by Canada.
One has to know his boundary; otherwise, he will put himself and those close to him in harms way. If that person happens to be the command in chief of the most powerful country, we had Iraq War.