What you're left with is the flimsiest of circumstantial cases: i.e., since Mohammed Atta is reported to have met with unnamed Iraqi intelligence officers, therefore Iraq must have helped the terrorists plan 9-11. That sort of flimsy circumstantial evidence wouldn't convict someone of a speeding ticket, much less serve as a basis for invading a sovereign nation.
By the same token, there's much more evidence that the 9-11 terrorists were directly financed by individuals within the Saudi government. When do we march on Riyahd?