The article analyzes one of the instruments of the U.S. expansion in the Caribbean in the first half of the 19th century - the creation of the states which the author determines as "temporary republics". These states were Republic of West Florida (1810), Republic of Florida (1812) and Republic of Texas (1836 - 1845). The author specifies four main features of the "temporary republics". Problem of the "temporary republics" is still actual in the early 21-st century in the former socialist countries.