There are numerous emergency communications organizations, some under ARRL, some under state or national governments, some independent.
ARRL
The American Radio Relay League (ARRL) is the largest membership association of amateur radio enthusiasts in the United States. ARRL is a non-profit organization ...founded on April 6, 1914….
The ARRL has approximately 161,000 members. In addition to members in the US, the organization claims over 7,000 members in other countries. The ARRL publishes many books and a monthly membership journal called QST.
The ARRL is the primary representative organization of amateur radio operators to the US government. It performs this function by lobbying the US Congress and the Federal Communications Commission. The ARRL is also the international secretariat of the International Amateur Radio Union, which performs a similar role internationally, advocating for amateur radio interests before the International Telecommunication Union and the World Administrative Radio Conferences.
Source: Wikipedia
ARES
In the United States and Canada, the Amateur Radio Emergency Service (ARES) is a corps of trained amateur radio operator volunteers organized to assist in public service and emergency communications. It is organized and sponsored by the American Radio Relay League and the Radio Amateurs of Canada.
Amateur radio operators belonging to ARES...have responded to local and regional disasters since the 1930s, including the attacks of September 11, 2001, and the category 5 storms Hurricane Katrina and Hurricane Michael.
Source: Wikipedia
RACES
The Radio Amateur Civil Emergency Service (RACES) is an emergency radio service authorized in Part 97.407 of the Federal Communications Commission (FCC) rules and regulations governing amateur radio in the United States…. ...RACES service was designed to provide a quicker and smoother transition in the event the President ever needed to silence the regular Amateur Radio Service again when invoking the War Powers Act of 1941.
Source: Wikipedia
Both ARES and RACES are groups founded by and operated under the American Radio Relay League or ARRL.
MARS
The Military Auxiliary Radio System (MARS) is a United States Department of Defense sponsored program, established as a separately managed and operated program by the United States Army and the United States Air Force…. The program is a civilian auxiliary consisting primarily of licensed amateur radio operators who are interested in assisting the military with communications on a regional and national level when access to traditional forms of communication may no longer be available. The MARS programs also include active duty, reserve, and National Guard units; and Navy, Marine Corps units.
Source: Wikipedia
AuxComm
Part of DHS National Emergency Communications
During crises or natural disasters, phones, computers and other major communications may no longer operate or may become so congested that service slows or even fails. Because amateur radio communications can work independently of these major systems, they continue to play the integral and reliable part in emergency communications they have played for over a century.
DHS’ Auxiliary Communications Field Operations Guide (AUXFOG) defines AuxComm as “an all-inclusive term used to describe the many organizations and personnel that provide various types of communications support to emergency management, public safety, and other government agencies."
The Office of Emergency Communications under DHS further states:
“Once the national Office of Emergency Communications was established under DHS in 2007, states gradually began combining their various groups of amateur radio emergency operators under an AuxComm umbrella for greater interoperability,” i.e. better communication “among jurisdictions, disciplines, frequency bands, and levels of government as needed and as authorized….
“Auxiliary Communications (AuxComm) covers a broad range of systems that could potentially be used during an incident to include: High Frequency (HF), Very High Frequency (VHF), Ultra High Frequency (UHF), satellite communications (SATCOM), microwave, Wi-Fi, digital, video, photos, Voice over Internet Protocol (VoIP), and other modes….
“Today, nearly all the States and territories have incorporated some level of participation by amateur radio auxiliary communication operators into their Tactical Interoperable Communications Plans and Statewide Communication Interoperability Plans; this allows them to quickly integrate the operators into response efforts, which can strengthen communications and operations during incidents of any scale.”
AuxComm is not a standard ICS position but is made up of amateur radio operators that provide auxiliary support to emergency management.
The AUXFOG manual adds:
“AuxComm services are typically voluntary, and are commonly provided by amateur radio communicators, but may also include other volunteer organizations which have established relationships with the government organizations they support. AuxComm services include emergency, backup, or supplemental communications support to government or non-government agencies during unexpected emergencies, planned events, or training exercises.
AuxComm personnel are commonly utilized in Emergency Operations Centers (EOCs) [and] are often used in catastrophic events when communications infrastructure has failed or has been compromised.”