Since, there is no "official cannon" on the above topic; I figure I'd give this little known "Van Buren" organization, a history.
2076: Following the Annexation of The Dominion of Canada, and the continued threat of communist saboteurs, the United States Government creates the Department of Homeland Security, with the stated goal of defending the United States against Canadian Terrorism, and Communist Infiltration.
2076: Now under DHS, the United States Customs Service, The US Coast Guard, The US Secret Service, The United States Immigration and Naturalization Service, The United States Border Patrol, and the Federal Protective Service are given the additional mandate of forming UnAmerican activities sections, whose primary purpose is to provide a singular purpose Special Response Team (SRT), tasked with matters which directly relate to Canadian Terrorism, or Communist Sabotage.
The Newly created sub-units are:
USCS: UnAmerican Activities Point of Entry Special Operations Group
USCG: UnAmerican Activities Special Boarding Unit
USSS: UnAmerican Activities Defector Special Protective Section
USINS: UnAmerican Activities Immigration Enforcement Unit
USBP: UnAmerican Activities Special Border Tactical Unit
USFPS: UnAmerican Activities High Value Asset Protection Unit
Notable Events:
The USCS POESOG foils an attempted hijacking at LaGuardia Airport.
The USCG SBU intercepts an Australian ship running guns to Vancouver, BC.
The USSS DSPS takes into custody a senior ranking communist infiltrator.
The USINS IEU raids an apartment in Manhattan, arresting a senior Canuck Terrorist and foiling a plot by Canadian dissidents to bomb the Statue of Liberty.
The USBP SBTU captures five Chinese saboteurs attempting to illegally cross the Rio Grande.
USFPS HVAPU foils an attempted communist saboteur attack on Los Alamos National Laboratory.
2077: In light of the continued war with China, and the added stress and strain of maintaining UnAmerican Activities Sections, the President of the United States, under the advice of the Director of Homeland Security, issues an executive order, thereby instituting the creation of a new federal law enforcement agency, the UnAmerican Activities Force. The UAF, absorbed the functions of the former UnAmerican Activities sections, and distinguished itself in numerous operations against communist saboteurs (the most prominent being the "Hoover Damn Incident".