The USA is the world's foremost economic and military power, with global interests and an unmatched global reach.
America's 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 defence spending put together.
The country is also a major source of entertainment: American TV, Hollywood films, jazz, blues, rock and rap music are primary ingredients in global popular culture.
The United States originated in a revolution that separated it from the British Crown. The constitution, drafted in 1787, established a federal system with a division of powers that has remained little changed since its inception.
President: Joe Biden
Democrat candidate Joe Biden defeated Republican President Donald Trump to win the presidency in the 2020 election. A former vice-president with decades of experience in Congress, Mr Biden campaigned on a platform of promoting national unity after the divisive presidency of Mr Trump, a right-wing businessman, and re-engaging with international diplomacy.
The US has the most highly-developed mass media in the world. Its dramas, comedies, soaps, animations, music videos and films have a global audience and are staple fare for broadcasters worldwide.
Television is the most popular medium, although the amount of content consumed via live broadcast TV is falling as video-on-demand platforms flourish.
The US is the home of the internet, and access is unrestricted.
1565 - First permanent European settlement in North America.
17th-18th centuries - Hundreds of thousands of Africans brought over and sold into slavery to work on cotton and tobacco plantations.
1775 - American Revolution: George Washington leads colonist Continental Army to fight against British rule.
1787 - Founding Fathers draw up new constitution for United States of America.
19th century - Residual resistance by indigenous peoples crushed as immigration from Europe assumes mass proportions, with settlers moving westwards.
1861-1865 - US Civil War: Federal forces defeat the Confederate pro-slavery states in the South. Slavery is abolished.
1929-33 - Some 13 million people become unemployed after the Wall Street stock market crash triggers what becomes known as the Great Depression.
1941 - Japan attacks the US fleet at Pearl Harbour in Hawaii, precipitating the US entry into World War Two.
1954 - Racial segregation in schools becomes unconstitutional; start of campaign of civil disobedience to secure civil rights for Americans of African descent.
2001 - Co-ordinated suicide attacks on various high-profile targets by the al-Qaeda jihadist group, prompting the US to embark on a ''war on terror'' that includes the invasion of Afghanistan and Iraq.
2008 - Barack Obama is elected the first black president of the United States.
2016 - Reality TV host and property tycoon Donald Trump regains the presidency for the Republicans on a populist platform.