详细解释:美国, 美利坚合众国, 美国陆军
英语解释：
名词 usa:
North American republic containing 50 states - 48 conterminous states in North America plus Alaska in northwest North America and the Hawaiian Islands in the Pacific Ocean; achieved independence in 1776同义词：United States, United States of America, America, the States, US, U.S., U.S.A.