They didn't have to be a threat to the US. 12 years of UN Security Resolutions said we had a right to go in, and the UN validated the war anyway.
What about Saddam being a threat to his people?
Should 30 million lives not count for anything?
And if 9/11 taught us anything, it is that people who attack our country likely won't with ICBMs. When leaders of nations openly support terrorism, as Saddam did, I think they have to be prepared for consequences.