First, I have to say that this is a long story and evidently not a common one.
My father was born in Canada. His father was a U.S. soldier stationed there in 1945. At the age of one, my father and his parents were brought back home. My father was drafted and fought in Vietnam. He has a social security number, has paid Social Security taxes all his life.
He is now 66 years old and being told that he is not a citizen of the U.S. We have been unsuccessful in finding a U.S. Birth Certificate, however, we were able to find his certificate of birth in Canada and his mother's and father's marriage license stating their address in Kentucky.
Everyone is giving my father the run-around. He went to the INS (not sure if that's right?) and the VA for help months ago. They were supposed to be conducting an investigation, but every time he calls to check on it, they take the same information again and promise, yet again that they will get back to him.
Until this happened, we had no clue that he was not a U.S. citizen!!! He fought for the U.S. in Vietnam, he has lived here for more than 65 years!
What can we do? Who can we talk to for help?
Citizenship and Social Security
We focus on Social Security and not immigration issues, so we won't be able to help much on this.
Here is a link indicating documents the SSA wants for proof of citizenship :
http://www.ssa.gov/hlp/isba/10/hlp-isba005-ctzn.htm
From that link, if your father has a US passport -- even an expired one (from Vietnam service?) that may be sufficient to prove citizenship.