Citizenship in the United States is a legal marker denoting political membership in the United States that entails specific rights, privileges, and duties. Citizenship is understood as a "right to have rights" since it serves as a foundation for a bundle of subsequent rights, such as the right to live and work in the United States and to receive federal assistance.

There are two primary sources of citizenship: birthright citizenship, in which a person is presumed to be a citizen provided that he or she is born within the territorial limits of the United States, and naturalization, a process in which an immigrant applies for citizenship and is accepted. These two pathways to citizenship are specified in the Citizenship Clause of the Constitution's Fourteenth Amendment which reads:

National citizenship signifies membership in the country as a whole; state citizenship, in contrast, signifies a relation between a person and a particular state and has limited application, generally, with some exceptions being that state citizenship may affect (1) tax decisions and (2) eligibility for some state-provided benefits such as higher education and (3) eligibility for state political posts such as U.S. Senator.

The United States of America (commonly abbreviated to the United States, the U.S., the USA, America, and the States) is a federal constitutional republic comprising fifty states and a federal district. The country is situated mostly in central North America, where its forty-eight contiguous states and Washington, D.C., the capital district, lie between the Pacific and Atlantic Oceans, bordered by Canada to the north and Mexico to the south. The state of Alaska is in the northwest of the continent, with Canada to the east and Russia to the west, across the Bering Strait. The state of Hawaii is an archipelago in the mid-Pacific. The country also possesses several territories in the Pacific and Caribbean.

At 3.79 million square miles (9.83 million km²) and with over 312 million people, the United States is the third or fourth largest country by total area, and the third largest by both land area and population. It is one of the world's most ethnically diverse and multicultural nations, the product of large-scale immigration from many countries. The U.S. economy is the world's largest national economy, with an estimated 2011 GDP of $15.1 trillion (22% of nominal global GDP and over 19% of global GDP at purchasing-power parity). Per capita income is the world's sixth-highest.

John Sidney McCain III (born August 29, 1936) is the senior United States Senator from Arizona. He was the Republican presidential nominee in the 2008 United States election.

McCain followed his father and grandfather, both four-star admirals, into the United States Navy, graduating from the U.S. Naval Academy in 1958. He became a naval aviator, flying ground-attack aircraft from aircraft carriers. During the Vietnam War, he was almost killed in the 1967 USS Forrestal fire. In October 1967, while on a bombing mission over Hanoi, he was shot down, seriously injured, and captured by the North Vietnamese. He was a prisoner of war until 1973. McCain experienced episodes of torture, and refused an out-of-sequence early repatriation offer. His war wounds left him with lifelong physical limitations.

He retired from the Navy as a captain in 1981 and moved to Arizona, where he entered politics. Elected to the U.S. House of Representatives in 1982, he served two terms, and was then elected to the U.S. Senate in 1986, winning re-election easily four times, most recently in 2010. While generally adhering to conservative principles, McCain at times has had a media reputation as a "maverick" for his willingness to disagree with his party on certain issues. After being investigated and largely exonerated in a political influence scandal of the 1980s as a member of the Keating Five, he made campaign finance reform one of his signature concerns, which eventually led to the passage of the McCain-Feingold Act in 2002. He is also known for his work towards restoring diplomatic relations with Vietnam in the 1990s, and for his belief that the war in Iraq should be fought to a successful conclusion. McCain has chaired the Senate Commerce Committee, opposed spending that he considered to be pork barrel, and played a key role in alleviating a crisis over judicial nominations.