The main ways to obtain the citizenship are by birth in the United States, by having an American parent, by naturalization or derivation. Each way has different requirements. Examine them separately.
We know that all those who are born in the United States are American citizens. There is just one exception: the children of foreign parents who are temporarily in the United States working as diplomats for the government of another country do not get the U.S. citizenship like the rest.
The American citizenship for those who are born in the country is protected by the 14th Amendment of the Constitution.
In these cases, regardless of the immigration status of the parents, if a baby is born in the United States or one of its territories (such as Puerto Rico), the child is American, even if one or both parents are undocumented.
American Citizenship by Naturalization
Naturalization is when a foreigner obtains the citizenship through an application.
When an immigrant, who is already a legal permanent resident, has been in the United States for more than five years and has obtained the green card or has been married to an American for three years, it is common to apply for the citizenship.
Naturalized citizens acquire basically the same rights of those who are citizens by birth. The only difference is that they cannot aspire to be president of the country, a reserved privilege to those known as “natural born citizens”.
Automatic Derivative Citizenship for the Children of Naturalized Citizens
When a person acquires the American citizenship by naturalization, his or her children automatically become U.S. citizens if they are under 18, are legal permanent residents (they hold their own residence card), and live with their naturalized mom or dad (the parent must have the physical and legal custody of the children).
Adopted by American Citizens
Children who are born abroad and are adopted by American citizens acquire, in almost all cases, their parents’ nationality.
Born Abroad when Parents Are American
People who are born in another country are American from the moment of birth if their father or their mother or both are American. This can be accomplished as long as a number of very strict requirements (which vary if both parents are citizens or only one of them, or if they are single or married) are met.
Puerto Rico and Other Territories
People who are born in Puerto Rico, the U.S. Virgin Islands, Guam and the Northern Mariana Islands are citizens from the moment of birth. They also meet the requirement “natural born”, and could even run for president of the United States.
By contrast, natives to American Samoa, Swains Island, and the Minor Outlying Islands, located in the Caribbean and the Pacific, are not citizens. They can only reside and work in the U.S., but they have no right to vote.