Which was a U.S. response to the terrorist attacks of September 11 2001?

Answer 1

Since the terrorists came from countries that were supposed to be US allies - Saudi Arabia and Egypt - the US retaliated by attacking Iraq that had nothing at all to do with the 9/11 attacks. The US also attacked Afghanistan, for which it had much better reasons since the Saudi Al-Qaeda organization had been allowed by Afghan authorities to set up training camps there. These two attacks are collectively known as the Second Gulf War.

The US then went on to occupy these countries for several years and tried to change them into democracies, which did not prove a success and cost thousands of US soldiers their lives in the process. In Iraq the removal of the Ba'ath Government and subsequent occupation mostly led (as predicted by many even before the Second Gulf War) to fierce fighting between Sunnite and Shia Muslims which in turn led to the rise of IS; in Afghanistan the ruling Taliban Muslims were removed from power, but not defeated as a force. Today they are again the de facto power brokers in much of southern Afghanistan.