Considerable progress has been made with regard to the coordination and communication among agencies responsible for preventing and responding to terrorism directed against the United States and its interests since 2001. All or parts of 22 federal agencies that were previously independent, leading to a "silo" culture, have been combined under the Department of Homeland Security, for example. These include the Customs Service (formerly part of the Treasury Department), the Immigration and Naturalization Service (formerly part of the Justice Department), the Transportation Security Administration (formerly part of the Transportation Department), and the Federal Emergency Management Agency (formerly a standalone group) (U.S. Department of Homeland Security 2012).

While combining these agencies has led to greater coordination and communication, difficulties remain, particularly with regard to domestic terrorism acts. This includes accepting the definition of what constitutes domestic terrorism as well as working with local and regional agencies in coordinating responses. Challenges also arise when dealing with international terrorists who may have operations and operatives outside the United States planning operations within the United States. In other cases, such as with the attack on the consulate in Libya, outside interests attack American interests in foreign countries, further complicating the issue of coordination and communication (Bouazza 2012).