The world has good reason to be afraid of the U.S. ... witness Iraq and the subsequent invasion for oil. Anyone that has anything the U.S. wants should be afraid. (Canada you have lots of fresh water ... hmmm)   

There might also be a political reason for invading Iran: elections in 2008. The rationale being, you don't want to change horses in the middle of the stream. If this scenario is feasible, then there may be some sort of strike against Iran around 2007 - giving Bush some time between now and then to conjure a justification out of thorough and reliable "intelligence reports" (hey if it worked once it can work again) ...

So if Bush embroils us in some sort of "intervention" in Iran, around election time the theme can be played that another Republican administration is essential to see this thing through to the end.

Just a thought.