USA is the abbreviation of the United States. The United States of America, referred to as the United States, is a Federal Republic constitutional country composed of Washington, D.C., 50 states, Guam and many other overseas territories. It covers an area of 9.63 million square kilometers (plus the sovereign part of the United States in the Great Lakes and the area of coastal waters such as estuaries, harbors and inland seas).
North America was originally a settlement of Indians. At the end of the 15th century, Spain, the Netherlands and other countries began to immigrate here, while Britain came from behind. In 1773, Britain had established 13 colonies. In 1775, the North American people's war of independence against the British colonists broke out.
On July 4, 1776, the Second Continental Congress was held in Philadelphia, with George Washington as commander-in-chief. The declaration of independence officially announced the establishment of the United States of America. In 1788, after the war of independence, George Washington was elected the first president of the United States.
After the civil war, the capitalist economy of the United States rose rapidly. In the early 19th century, the United States began to expand abroad. After World War II, its national strength increased greatly. It is the only "hegemonic" superpower in the world.
On November 4, 2020, the United States officially withdrew from the Paris Agreement and became the only party to withdraw from the Paris agreement so far.