Acquisition of citizenship at birth:

The requirements for citizenship at birth for children born outside of the United States depend upon the marital status of your parents, whether your mother, father, or both parents were United Stated citizens, and for how long and at what age the United States citizen parent lived in the United States before you were born.

Derivative citizenship through the naturalization or U.S. birth of one parent:

Derivative citizenship is citizenship given to children through the naturalization of parents or, sometimes, to foreign-born children adopted by United States citizen parents, if certain conditions are met before you are 18. The requirements for automatic U.S. Citizenship after birth – But Before the Age of 18 depend upon when you were born or adopted by your U.S. citizen parent.