What event prompts America to declare war on Afghanistan?Discuss the reasons involved ?

On September 11, 2001 three planes are flown into buildings in New York City. This prompts the Americans to go into Afghanistan to attack the Taliban and find Osama bin Laden. Tariq tells Laila that Afghanistan will not turn over Osama bin Laden, because they are claiming to adhere to a Pashtun custom of hospitality, but Tariq knows that the Taliban are distorting the custom. Laila and Tariq learn that President Bush declares the war on terror, naming Afghanistan as an enemy.