If a man is a citizen of the United States, then he was

Question

born in the United States. Sam was not born in the
United States. Therefore Sam isn’t a citizen of the
United States?

Answer 1

Not necessarily. There are other ways to become a citizen, or to be born a citizen. The first ststement is not correct; no fact can be deduced from false statement.

Other ways to be be a citizen without being born here:
(1) become naturalized
(2) be the child of at least one American citizen parent, although born outside the country.
(3) Be born in Puerto Rico or Guam

Answer 2

Drwls is, of course, correct in the various ways of becoming a citizen.

I interpret your question differently. Your initial statement is wrong. However, if it were correct, then your argument would be true.