USA

The United States of America is a constitutional federal republic comprising fifty states and a federal district. The country is situated mostly in central North America, lie between the Pacific and Atlantic Oceans, bordered by Canada and Mexico. The state of Alaska is in the northwest of the continent, and the state of Hawaii is an archipelago in the mid-Pacific. The United States also possesses five major territories with indigenous populations: Puerto Rico and the United States Virgin Islands in the Caribbean; and American Samoa, Guam, and the Northern Mariana Islands in the Pacific. At 9.83 million km² and with more than 300 million people, the United States is the fourth largest country by total area, and third largest by population. The United States is one of the world's most ethnically diverse nations, the product of large-scale immigration from many countries. The U.S. economy is the largest national economy in the world.

The indigenous peoples of the U.S. mainland, including Alaska Natives, are thought to have migrated from Asia. They had been living in this land for more than 10000 years. After Columbus found the America continent in 1492, European settlers started to move to this new land. Over two hundred years of struggle and fighting, English settler became most successful among all European settlers. The nation was founded by thirteen colonies of Great Britain located along the Atlantic seaboard. Proclaiming themselves "states," they issued the Declaration of Independence on July 4, 1776. The rebellious states defeated Great Britain in the American Revolutionary War.

In the nineteenth century, the United States acquired land from France, Spain, the United Kingdom, Mexico, and Russia, and annexed the Republic of Texas and the Republic of Hawaii. Disputes between the agrarian South and industrial North over states' rights and the expansion of the institution of slavery provoked the American Civil War of the 1860s. The North's victory prevented a permanent split of the country and led to the end of slavery in the United States. The Spanish-American War and World War I confirmed the nation's status as a military power. In 1945, the United States emerged from World War II as the first country with nuclear weapons, a permanent member of the United Nations Security Council, and a founding member of NATO. In the post–Cold War era, the United States is the only remaining superpower—accounting for approximately 50% of global military spending—and a dominant economic, political, and cultural force in the world.