What State were you born in?
Unless you were born in one of the thirteen original states, your citizenship is a result of an act of Congress.
Let's say you were born in California, for example. None of the people of California were United States citizens before an act of Congress made them that way.
In fact, this covers most of the population of the United States. More than two-thirds of Americans - including everybody born in the State of Texas - were made citizens by an Act of Congress.
I was born in Ohio to two U.S. citizen parents, who were also born on U.S. soil, and I am a citizen under the 14th Amendment of the U.S. Constitution. Congress cannot revoke my citizenship without my consent merely by passing legislation.