Luke Angel, 17, of Silsoe, was investigated after he expressed his dislike of President Barack Obama and the US Government.
Bedfordshire police, who then visited Luke, said the e-mail was full of abusive and threatening language.
“He was told that he wouldn’t be able to go to America,” they added.
A spokeswoman said it was a case of a boy “being silly” and no criminal action was being taken.
“We were informed by the Metropolitan Police and so we went round to see him,” she said.
“He said ‘oh dear, it was me’.”
He told police he could not remember exactly what he had written in the e-mail. – BBC