re: those who were responsible for 9/11 had no links with Iraq.
Any country has to know that to stage a WMD attack on the US would bring massive retaliation on the scale that would make shock and awe seem like a walk in the park and certain death to its leadership. That kind of threat would not only keep direct attacks from being launched from within Iraq but would be a huge deterrence as well to them being the suppliers to some terrorist organization if the tiniest thread of evidence linked them to it. A WMD attack would bring worldwide condemnation and pretty much a green light for the US to go after whoever it felt was guilty.
Didn't stop Afghanistan, did it?