First, you're conflating Afghanistan and Iraq. If you think that the US would sit by while Mullah Omar supported Al Qaeda camps after 9/11, you're greatly mistaken. Though the war in Afghanistan should have never entered a nation-building phase, it's hard to lump it with a war of choice in Iraq.

Also, I believe that you meant Colin Powell speaking to the UN. I don't believe VP Cheney made any presentations to the UN in the run up to the Iraq War.