The United States of America is a country located primarily in North America, consisting of 50 states, a federal district, five major unincorporated territories, nine Minor Outlying Islands, and 326 Indian reservations. The country is the world's third-largest by both land and total area. The political system of the United States is based on the Constitution of 1787, which established a federal system with a division of powers that has remained little changed since its inception. The country is a constitutional federal republic with a strong democratic tradition, and the chief of state and head of government is the president. The United States is the world's foremost economic and military power, with global interests and an unmatched global reach. Its gross domestic product accounts for close to a quarter of the world total, and its military budget is reckoned to be almost as much as the rest of the world's defense spending put together. The country is also a major source of entertainment, with American TV, Hollywood films, jazz, blues, rock, and rap music being primary ingredients in global popular culture. The official language of the United States is English, but it has no official national language. The United States has an advanced mixed economy in which there is a variety of private freedom, combined with centralized economic planning and government regulation