The FBI asked local cops to tell college student Luke Angel, 17, that his drunken insult was "unacceptable."
Angel claims he fired off a single e-mail criticizing the U.S. government after seeing a television program about the 9/11 attacks.
He said, "I don't remember exactly what I wrote as I was drunk. But I think I called Barack Obama a pr*ck. It was silly -- the sort of thing you do when you're a teenager and have had a few."
Angel, of Bedford, in central England, said it was "a bit extreme" for the FBI to act.
"The police came and took my picture and told me I was banned from America forever. I don't really care but my parents aren't very happy," he said.
A Bedford Police spokesman confirmed they had spoken to Angel about the e-mail. Officers will take no criminal action.
Joanne Ferreira, of the U.S. Department of Homeland Security, said there are about 60 reasons a person can be barred from visiting America.
She said, "We are prohibited from discussing specific cases."