when were the states of italy united
U.S.-ITALY RELATIONS. The United States established diplomatic relations with Italy in 1861 following the unification of most of the peninsula into one state. In 1941, Italy -- with the other World War II Axis powers Germany and Japan -- declared war on the United States.U.S. relations with Italy were reestablished in 1944.taly maintains an embassy in the United States at 3000 Whitehaven Street, NW, Washington, DC 20008 (tel. 202-612-4400). More information about Italy is available from the Department of State and other sources, some of which are listed here: