The terrorist attacks on September 11 , 2001 affected American perspectives on many issues , including immigration . A total of 20 foreign terrorists were involved , 19 of whom took part in the attacks that caused the deaths of 2,977 victims , most of them civilians . The terrorists had entered the United States on tourist or student visas . Four of them , however , had violated the terms of their visas . The attack exposed long-standing weaknesses in the U.S. immigration system that included failures in the areas of visa processing , internal enforcement , and information sharing
terrorist attacks on September 11 , 2001
September 11 attacks
History of laws concerning immigration and naturalization in the United States