U.S.C.I.S. (United States Citizen and Immigration Services) handles all immigration processes in the U.S. http://www.uscis.gov
Immigration through adoption, or “Intercountry adoption,” refers to the adoption of a child born in one country by an adoptive parent living in another country. USCIS plays a key role in the intercountry adoption process.
United States immigration law provides three different processes through which someone may immigrate on the basis of an intercountry adoption. An individual may immigrate under one of these provisions only if the individual’s adoption meets all the requirements of that specific process.
Two separate processes apply only to children adopted by U.S. citizens. The child may immigrate immediately after the adoption or may immigrate to the U.S. to be adopted here.