Final answer:
The 9/11 Commission Report revealed missed opportunities by the FBI to investigate Zacarias Moussaoui before the attacks and failures by both the Clinton and Bush administrations to adequately respond to terrorist threats. It also clarified the lack of a connection between al-Qaeda and Iraq, and the absence of WMDs there.
Step-by-step explanation:
The 9/11 Commission Report's Revelations
The 9/11 Commission Report revealed several missed opportunities that could have potentially prevented the tragic attacks of September 11, 2001. One of the critical oversights was the failure of the FBI to fully investigate Zacarias Moussaoui, who had raised suspicions at a flight school in Minnesota. Despite being arrested for a visa overstay, his connections and belongings were not thoroughly searched until after the attacks.
The report also highlighted failures by both the Clinton and Bush administrations to respond adequately to the threat posed by al-Qaeda and Osama bin Laden, as well as the lack of meaningful connection between al-Qaeda and Iraq, contrary to what was believed at the time. Furthermore, subsequent investigations found no credible evidence of weapons of mass destruction (WMDs) in Iraq, which had been one of the principal justifications for the war.
Post-9/11, the American public's opinions about Muslims generally became more favorable, possibly influenced by President Bush's appeals not to blame Muslims as a whole for the attacks. This response, among many others, shaped the direction of American policy and perception in the years following the events.