One, it's only a fairy tail if it was intentional dishonesty. That was not the case. pretty much everyone, even in the US congress, including Bill, Hillary, Schumer, Pelosi, and all of the other usual suspects believed that the Saddam Regime had vast stocks of WMDs View the video at the bottom of this post. And it was up to the Iraq regime to prove that they had destroyed wmd material that previous inspectors had found and the regime had admitted to. That responsibility includes immediate access to sites the inspectors show up at. Two, the US, never in it's history has been required to get a permission slip from the UN to go to war with anyone. And the UN failed in it's responsibilities as they failed to enforce the many versions of sanctions against the Iraq regime. If one failed, they would just pass another, then another, and another, so on.
Saddam was more of a danger to our allies, however with the threat he represented to Kuwait and the Saudis, he was in effect a threat to the entire free world. The 1991 war was about Iraq overrunning Kuwait and then lining up on the Saudi border. He was lined up to take control of roughly 50% of the world's known oil reserves at the time. With that much control over oil, he could have on a whim wrecked the economies of most of the free world. Russia uses sales of natural gas in much the same way in the baltic states. Even without the wmds Bush had all the justification he needed to invade iraq as they were in clear violation of all the agreements they signed onto to end the 1991 war.
But then the thing about support for wars is about how we go about them. Americans have supported virtually every war we have been involved in. The problem is when they go long. The elder Bush enjoyed full support for the 1991 war. it was quick and clean with clear objectives. he enjoyed something like 80% approval ratings when the war ended. The 2003 initially had broad public support, even from the democrats until it went long. Even the Vietnam War had initial support. if Bush had employed the surge strategy as soon as the insurgency popped up, I doubt his approval ratings would have suffered. The Afghanistan war is no longer popular because it has now gone on longer then any other war we have been in.