The United States (U.S.) or America,

 The United States (U.S.) or America

The United States (U.S.) or America, is a federal republic consisting mainly of North America. It is a federal republic with 50 states and a federal capital district, Washington, D.C. The 48 continuous states border Mexico to the south and Canada to the north, with the semi-exclave Alaska in the northwest and the Hawaiian archipelago in the Pacific Ocean. The United States also claims sovereignty over five large island coThe United States of America (USA)untries and many unoccupied islands in Oceania and the Caribbean.[j] It is a megadiverse nation, with the third-largest land area in the world[c] and the third-largest population, at over 340 million. Paleo-Indians came to North America from North Asia more than 12,000 years ago and established different civilizations.

Spanish colonization founded Spanish Florida in 1513, the initial European colony in the current continental United States. British colonization then resulted from the 1607 establishment of Virginia, the first of the Thirteen Colonies. Enslaved Africans' forced migration provided the workforce to maintain the plantation economy of the Southern Colonies. Conflicts with the British Crown regarding taxation and no representation in parliament ignited the American Revolution, culminating in the Declaration of Independence on July 4, 1776. The 1775–1783 Revolutionary War victory resulted in international acceptance of U.S. sovereignty and drove westward expansion at the expense of native residents. With the admission of more states, a North–South divide on slavery prompted the Confederate States of America to seek secession and wage war on the Union during the 1861–1865 American Civil War. With victory by the United States and reunification, slavery was outlawed throughout the nation. The nation had become a great power by 1900, status that was cemented after its participation in World War I. After Japan attacked Pearl Harbor in 1941, the U.S. became involved in World War II. Its aftermath left the U.S. and the Soviet Union competing as rival superpowers, vying to dominate in terms of ideology and worldwide influence during the Cold War. The collapse of the Soviet Union in 1991 concluded the Cold War, and the U.S. emerged as the world's lone superpower. The national government of the U.S. is a presidential constitutional federal republic and representative democracy with three distinct branches: legislative, executive, and judicial.

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It has a bicameral national parliament consisting of the House of Representatives (a lower chamber proportional to population) and the Senate (an upper chamber proportional to equal representation to each state). Federalism reserves considerable autonomy for the 50 states. There are also 574 Native American tribes that enjoy sovereignty rights, with 326 Native American reservations. Since the 1850s, American politics have been shaped by the Democratic and Republican parties, whereas American values are rooted in a democratic heritage derived from the American Enlightenment movement. Developed, the U.S. is highly ranked in economic competitiveness, technological innovation, and higher education.

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Responsible for producing more than a quarter of nominal worldwide economic production, its economy has been the largest in the world since roughly 1890. It is the richest nation, with the highest per capita disposable household income among OECD members, although its wealth disparity is among the highest of the member nations. Influenced by centuries of immigration, the U.S. culture is multi-diverse and internationally impactful. Spending over one-third of the world's military expenditure, the nation boasts one of the world's most powerful militaries and is a nuclear state. A member of many international organizations, the United States is a key participant in world political, cultural, economic, and military developments.