The Taliban protected Al Queada prior to 9/11, too. The reason we didn't attack the Taliban prior to 9/11 was because we concluded, wrongly, that it wasn't a threat to us. Fortunately, having learned our lesson the hard way, we didn't repeat this mistake with respect to Iraq.
As for the degree of the threat, I would agree that there are other threats of varying degrees. Indeed, one reason for taking action against Iraq now rather than later was to prevent Iraq from becoming the next North Korea. I don't see how allowing Saddam to proceed with his WMD program (even to the point of acquiring nuclear weapons) makes the United States a safer place rather than a more dangerous place. Put another way, you don't cure a smaller malignant tumor like Iraq by allowing it to grow into an even bigger malignant tumor. You cure it by removing it while you can.
That is sophistry. What is your argument? That because we failed to see the threat of 9/11 from the AQ forces residing in the Afghan Taliban regime that we are now, somehow, empowered to destroy any percieved threat anywhere at anytime on the Globe? That is precisely what scares the world about the USA. And what is driving us into over extension and creating more terrorists.
We were attacked on 9/11 - not with WMD's (a Threat I lived under most of my entire life and so did my parents from madmen like Stalin and Kruschev and Brezhnev and Mao) but with box cutters! With box cutters.