Not the US responsibility, but UN responsibility
that reason was that Iraq was in violation of numerous declarations regarding WMDs from the original cease fire to the last resolution.
Bush implied that Iraq had WMD and was imminent threat to US safety. That Saddam was in violation of UN resolutions is/was/should have been an UN issue.
Vigilante actions should not be encouraged.
When they took the Fourth Amendment, I was quiet because I didn't deal drugs.
When they took the Fifth Amendment, I was quiet because I was innocent.
When they took the Second Amendment, I was quiet because I didn't own a gun.
Now they've taken the First Amendment, and I can't say anything about it.