The United States took military action against the Taliban due to the attacks on the World Trade Center in 2001 by al Qaeda. Osama bin Laden was determined to have had connections to the movement (however tenuous or extremist they may have been) and the movement itself oftentimes encouraged hostilities against Western states due to their century-long period of interference in Middle Eastern affairs.
Led to the creation of a two chamber congress. Also created was the House of Representative which is determined by a state's population
