@Finn dAbuzz,
I think Finn's summing up is pretty accurate. As to Tico's question I think a Bush denial would have at least stalled and most likely prevented the invasion.
Think about what a Bush statement saying unequivocally that Saddam had no involvement in 911 would have had internationally. I can't speak for the mood in the USA at the time (although I am aware there was a significant, if minority, protest movement against the impending invasion) but in other members of the 'coalition of the willing' the majority of the populations were against the invasion. The British, significantly, and the Australians, less signficantly, had huge protests against the impending invasion but in both cases their leaders pushed it through in any case (often misrepresenting the facts if not outright lying).
I don't think they would have been able to do that if Bush had said Hussein wasn't involved in 911. And I don't think the US would have gone it alone in defiance of the UN AND a number of key allies. I don't think a couple of Pacific Island Nations, some former soviet bloc countries and the odd African nation lending little more than moral support would have given Bush the legitimacy he craved.
I still remember 'Freedom Fries'.