WMD was a reason. Unfortunately, Saddam played the Ace, and fooled not only the US., but took you in as suckers in supporting HIS cause and not ours (which *was/is* for the good of the world, as well as his people) Using said WMD as terrorist weapons and/or selling them to these people was as much of a threat. It would have happened eventually, don't you think?
But no worries, we'll still protect your sorry futuristic butts, even without a "thanks".