<P> The United States of America ( USA ) , commonly known as the United States ( U.S. ) or America ( / əˈmɛrɪkə / ) , is a federal republic composed of 50 states , a federal district , five major self - governing territories , and various possessions . At 3.8 million square miles ( 9.8 million km ) and with over 324 million people , the United States is the world 's third - or fourth - largest country by total area and the third-most populous . The capital is Washington , D.C. , and the largest city by population is New York City . Forty - eight states and the capital 's federal district are contiguous and located in North America between Canada and Mexico . The state of Alaska is in the northwest corner of North America , bordered by Canada to the east and across the Bering Strait from Russia to the west . The state of Hawaii is an archipelago in the mid-Pacific Ocean . The U.S. territories are scattered about the Pacific Ocean and the Caribbean Sea , stretching across nine official time zones . The extremely diverse geography , climate , and wildlife of the United States make it one of the world 's 17 megadiverse countries . </P>
what type of government is in north america
federal republic