In my opinion, the failure was not Bush's; there WERE 17 UN sanctions being violated, and the Democrats supported the Iraq engagement. People can debate whether the intelligence Bush presented was credible best-available data or a believable lie, but that doesn't explain the majority of the 17 UN resolutions that were used as justification.
The failure was in not staying to secure the region, which is all on Obama. Given that we're still in Germany after 70 years, and still in South Korea after 60 years, why did we so quickly pull out of Iraq and Afghanistan while the region was so unstable? The answer is that Obama's loyalties are not with America's issues. A destabilized Middle East allowed Obama's team, the Muslim Brotherhood to fill the void.
George Bush did not topple Mubarak in Egypt, nor Ghaddafy in Lybia, nor Assad in Syria. That was all Obama's meddling to lay the foundation for the emergence of the Muslim Brotherhood. And then they turned on him.
-PJ
You can blame Obama for a lot of things, but this isn't one of them. When Obama removed the last U.S. military personnel from Iraq, he was simply meeting the terms of the agreement between the U.S. and Iraq that was signed in November 2008 by George W. Bush.