In fairness to creator Seth MacFarlane, tonight's episode of Family Guy was made and broadcast without his participation or approval, as he's part of the writer's strike. Perhaps the episode was just written sloppily and hastily by the scabs. Whatever the cause, the plot turned on a point of law that was utterly erroneous.
To recap the episode, at a Veteran's Day parade Peter begins to feel hyper-patriotic, and goes on a campaign against immigrants. His HR director at work agrees that she should check on everyone's legal status, so Peter asks his mother for his birth certificate to prove that he was born a U.S. citizen. She tells him that after realizing his biological father was a drunk Irishman, she went to Mexico for an abortion, but ended up giving birth to him there. Peter's mother was too embarrassed to let anyone know about this, so she never did the paperwork for his citizenship, and tells him that he therefore is not a citizen.
As probably every law student, recent graduate and immigration lawyer watching the episode yelled out, that's incorrect. The child of a married U.S. citizen who is born overseas is a citizen at birth, and so is the child of an unmarried U.S. citizen mother. No paperwork is necessary under 8 U.S.C. 1401(g). INS v. Nguyen examined whether the rule that the child of an unmarried U.S. citizen father did not have citizenship at birth was sex discrimination, and ruled in a 5-4 decision that it was not. (Bad Stevens! Bad!)
The only way the episode could have made the plot point work would be to state or imply one of the following: that Peter had been born prior to May 24, 1934, at which time only U.S. citizen fathers, but not mothers, could transmit citizenship to their children; that Peter had been born before December 24, 1952 and his mother had not resided in the U.S. for at least 10 years, at least five of which were after attaining the age of 16 years; or that Peter had been born before November 14, 1986 and his mother had not resided in the U.S. for at least 10 years, at least five of which were after the age of 14. This would work quite easily if Peter's mother had been under 21 at the time of his birth, at which point it would have been impossible for her to reside in the U.S. for five years after turning 16.
Had the episode stated that Peter at one point had citizenship but had lost it due to his overseas birth, this would work if he was born before October 10, 1978 and had spent less than two years in the U.S. between the ages of 14 and 28.
To see Family Guy screw up the law like this is disappointing after this bit.