How did the united states respond to the terrorist attack on september 11, 2001?

President Bush authorized Operation Enduring Freedom and invaded Afghanistan in response to the terrorist attack on September 11, 2001.

"Operation Enduring Freedom" is the official name that the United States Government gave to the Afghanistan War, as well as a number of smaller military actions, in the context of the "War on Terror."

After the September 11, 2001 attacks, the U.S. government reacted immediately carrying out investigations, legislative changes, military action as along with restoration projects. As a result of investigations into the motivations and execution of the attacks, they declared War on Terrorism which resulted in the ongoing military engagements in Afghanistan and subsequently Iraq.