The United States of America is a constitutional federal republic composed of 50 states and a Federal Territory SAR countries, the East Atlantic Ocean, west Pacific, north of Canada, south of Mexico. The United States is a multi-cultural and multi-ethnic country; land area of more than 9.62 million square kilometers, ranking the world's third or fourth; the total population of over three hundred million people, ranking third in the world. July 4, 1776, the Continental Congress in Philadelphia formally adopted the Declaration of Independence, declaring the United States was born. Since 1870, the U.S. national economy, the highest in the world, is one of the five permanent members of UN Security Council, today's gross domestic product (GDP) of more than 20% of the world. The enormous influence of its economic, political, scientific, technological, military, entertainment and many other areas are to lead the world, is currently the world's only superpower.
U.S. global economic, political and military influence of its foreign policy direction has been the focus of world attention and discussion. U.S. diplomatic relations with the size of the largest in the world. Almost all countries have established in Washington, DC embassies and ambassador. Israel, Britain, Canada, Australia and Japan is considered the closest ally of the United States. Only a few countries did not establish formal diplomatic relations with the United States, including Cuba, Iran, North Korea, Somalia and Sudan. During the American Revolution, the United States and some European countries to establish diplomatic relations, to persuade France, Spain and the Netherlands to help fight the British. In the next reclamation years, the United States has been vacillating between pro-France, or pro-British two choices. At that time the United States is willing to interfere in European affairs, focused on the North American territory to open up. Weaken Europe's influence in Latin America and later to the Monroe Doctrine, in order to ensure control over the affairs of the Americas. The expansion policy of the United States has gradually led to war with Mexico and Spain, two games are the United States, claiming victory. In the Civil War, the United States has accused Britain and France support the southern secessionist Confederate States of America, and trying to occupation of Mexico, but after the Civil War, the United States a dominant position in North America would no longer have not received any challenge.