Throughout American history, the U.S. government’s need to conduct surveillance has been carefully balanced against the individual liberties protected by the Constitution. The events of 9/11 have been used as pretext to dramatically expand the government’s surveillance authorities and reinterpret the Constitution’s protections as inapplicable.
Prior to September 11th, the Foreign Intelligence Surveillance Act (FISA) allowed the government, in limited circumstances, to secretly wiretap Americans and obtain access to their electronic communications. Congress approved FISA in 1978 but on the condition wiretaps be predicated on a judge’s individualized determination that probable cause exists to suspect the American of knowingly aiding a foreign power or terrorist. Courts held that FISA passed constitutional muster based on these individualized protections.
Despite the FISA law, shortly after 9/11 the Bush Administration began monitoring Americans’ communications and conversations without FISA warrants and in violation of FISA’s individualized protections. For four years, the administration publicly claimed it had obtained warrants for all monitoring activities. After its warrantless surveillance was revealed in 2005, the administration argued it could set-aside FISA based on “inherent” presidential powers, or in the alternative, that Congress granted the administration implicit authority to ignore FISA by authorizing military force in Afghanistan. These claimed justifications were widely rejected by scholars. Regardless, in 2008 Congress essentially ratified the administration’s activities by authorizing the FISA court to approve electronic surveillance programs without individual court orders or showing of individual wrongdoing.
The specially created FISA court has issued more orders for electronic surveillance in the ten years since 9/11 than in the entire previous 22 years (more than 15,661 FISA orders approved since 2001 versus 13,102 between 1978 and 2000).
In addition to electronic surveillance, the U.S. government has used post-9/11 terrorist fears to expand its monitoring of U.S. citizens who have nothing to do with terrorism. For example, the FBI’s “Joint Terrorism Task Forces” and the Defense Department’s base “protection” staff have monitored peace groups with absolutely no tie to Al Qaeda, including pacifist Quakers and Catholics at the Thomas More Center in Pennsylvania. Under the guise of monitoring “terrorists,” federal and state agents have also monitored anti-nuclear activists and Pennsylvania residents concerned about the threat unregulated oil shale drilling poses to their water supply. The Patriot Act also expanded the Secret Service’s authority to charge protestors with “disruptive behavior” at “National Special Security Events” (NSSEs) like political conventions, despite the fact that the vast majority of expressions of political dissent have nothing to do with national security or terrorism. 
Americans have never lived in an environment where their everyday actions—so many of which are conducted electronically—may fall under such potentially intense and far-reaching scrutiny.