The full form of CPUSA is Communist Party of the United States of America. It’s used on Governmental ,Politics in United States

Communist Party of the United States of America (CPUSA), also called Communist Party USA, left-wing political party in the United States that was, from its founding in 1919 until the latter part of the 1950s, one of the country’s most important leftist organizations. Its membership reached its peak of 85,000 in 1942, just as America entered World War II; the CPUSA had rallied enthusiastically in favour of a Soviet-American war effort against Nazi Germany.

In 1919, inspired by Russia’s October Revolution (1917), two U.S. communist parties emerged from the left wing of the Socialist Party of America (SPA): the Communist Party of America (CPA), composed of the SPA’s foreign-language federations and led by the sizeable and influential Russian Federation, and the Communist Labor Party of America (CLP), the predominantly English-language group. They were established legally but were soon forced underground. Although the two parties feuded and various factions broke away to establish competing communist groups, the Communist International encouraged the unification of those organizations. In 1922 the CPA merged with the United Communist Party (which had been established when the CLP joined a breakaway faction of the CPA) to create the legal and aboveground Workers Party of America (WPA). When the United Toilers of America, a group that adopted the same tactics as the WPA, combined with the latter organization, the party renamed itself the Workers (Communist) Party, finally settling on the name Communist Party of the United States of America in 1929.