English Defence League (EDL) leader Stephen Lennon, 30, pleaded guilty to possession of a false identity document with improper intention, contrary to the Identity Documents Act 2010, at Southwark Crown Court.
Lennon used a passport in the name of Andrew McMaster to board a Virgin Atlantic Flight from Heathrow to New York, but was caught out after his fingerprints were taken by customs officials.
He left the airport and entered the US illegally but left the country the following day, using his own passport to return to the UK.
More top news
White House budget officials outlined the information during a telephone call with reporters given on condition of anonymity.
A prison officer is to be charged with gross negligence manslaughter and misconduct in public office in relation to the death of an inmate.
The 2017 Oscars will be remembered as the year the wrong film got the best picture award, but it wasn't the first memorable mix-up.