Citizenship and Place Of Birth In The United States

The population of the United States in the 2020 census was 331.44 million people.

People Born In The United States

In the United States about 85.9% of the population consists of U.S. citizens born in the United States. 

There are some people born in the United States who are not U.S. citizens (basically children of certain diplomats), but they make up less than one in a million of the people born in the United States who reside in the United States at any given time (i.e. less than 285 people). Thus, roughly 99.9999% of the people in the United States who were born in the U.S. are U.S. citizens.

Foreign Born Americans

The remaining 14.1% of people who reside in the United States are foreign born. About 24.3% of the foreign born population of the United States was born in Mexico.

- U.S. Citizens Who Were Born Abroad

About 6.6% of people in the U.S. (about 21,875,000 people) are foreign born persons who are U.S. citizens. 

This is mostly made up of naturalized U.S. citizens (probably 6.0%-6.5% of the total U.S. population).   

Over the last ten years an average of about 740,000 people per year have been naturalized as U.S. citizens. Adult naturalized citizen break down demographically as follows;

The median years spent as an LPR for all citizens naturalized in FY 2021 was 7.3 years. The median years spent as an LPR varied by the citizens’ country of birth. The countries with the largest number of new citizens in FY 2021 . . . applicants from Mexico spent the longest time, with 10.7 years, and applicants from Nigeria spent the shortest, with 6 years.

About 13.9% of recently naturalized U.S. citizens were born in Mexico.

But about 0.1%-0.6% of the U.S. population (about 21,875 to 131,250 people), based upon my back of napkin estimates, are people born outside the United States who are U.S. citizens because one or both of their parents were U.S. citizens (under rather complicated rules). I have not been able to locate good direct statistics for the size of this population.

My estimate of the number of people who are U.S. citizens at birth who are born abroad is based in part upon the fact that at any given time, about 1% of U.S. citizens live outside the United States. This population is male biased due to the significant share of these U.S. citizens who are active duty military personnel serving abroad (a population that is about 82% male), and even female U.S. military personnel tend to receive a discharge from the military or to be in the U.S. rather than being deployed abroad when they give birth.

- Non-U.S. Citizens

About 7.5% of the people in U.S. are not U.S. citizens. About 4.3% of the people in the United States are foreign born people who reside in the U.S. pursuant to visa granted by the federal government, and about 3.2% of the people in the United States are foreign born people who are undocumented.

About 43% of non-U.S. citizens who reside in the United States are undocumented. About 47% of undocumented non-U.S. citizens who reside in the U.S. were born in Mexico.

About 6% of undocumented U.S. residents (about 0.2% of the U.S. population) are active participants in the DACA program. About 80.6% of DACA participants were born in Mexico.

About 47% of foreign born people in the United States are U.S. citizens, about 30% of of foreign born people in the United States are "documented" non-citizens, and about  23% of foreign born people in the United States (about 10.5 million) are "undocumented" non-citizens.