And because the hijackers were all Muslims, acute scrutiny in the immediate aftermath of the attacks was focused on Muslims or those who were perceived to be Muslims, with broader use of nationality-based screening and enforcement programs.
Equally interesting, though, is what did not occur after the terrorist attacks. Given the experiences in comparable chapters of U.S. history (with special programs directed at German-Americans in World War I, Japanese-Americans in World War II, and "communist radicals" after that war), a much stronger backlash against immigrants and Muslims was predicted after 9/11. The most dire of the predictions, though, did not materialize. There was no round-up or internment of Muslim-Americans; the targets of government actions were noncitizens, principally unauthorized immigrants. There also was no legislative effort in Congress to place a moratorium on legal immigration, or on immigration from certain countries.