America knows it fucked up. Now. If you go back and look at the events leading up to the invasion, however, America had no idea what it was getting into. That's the important part. Our representatives had so little information at the time it was staggering. They essentially had the words of Bush, Cheney, Rumsfeld, the infamous "it's a slam dunk case" comment by George Tenet regarding WMDs, and the Feith Gestapo. Congress didn't even know that Bush was spending Afghanistan money to upgrade Iraq staging points such as bases and airfields.
Cheney was pushing for an invasion well before 9/11 for fuck's sake. It was at the top of his post-election agenda. He was the greatest single force compelling Bush to act.
Even Powell, who harbored great doubts about such a conflict, was eventually convinced by the administration that it should be undertaken. He called Iraq "the Pottery Barn" because, as he told Bush, "if you break it, you own it."
Our good faith in our leadership bit us in the ass, but I'm not losing any sleep over it. It's not like we still deny we did anything wrong.