Your "Bush would have invaded regardless" is .........................
I am not certain and I have no evidence .
But I hope he would have.
Would you turn your back on an enemy to fight a smaller enemy?
Saddam was ordering his AA batteries to fire at our aircraft months after we had demonstrated that this was not working.
I think that it would have been stupid to attack Afghanistan without reducing the threat on the flank that Saddam represented.
If he was so eager to stab at us in ways that cost him trained AA radar operators and expensive missile launchers , I imagine him not passing up a chance to truly cost us by cutting our extended lines of supply that would be running within his reach.