The court heard that Lennon, who had previously been refused entry to the US, used his friend's passport to travel to the country in September.He used a self check-in kiosk to board the Virgin Atlantic flight at Heathrow, and was allowed through when the document was checked in the bag drop area.
But when he arrived at New York's JFK Airport, customs officials who took his fingerprints realised he was not Mr McMaster.
Lennon was asked to attend a second interview but left the airport, entering the US illegally.
He stayed just one night and travelled back to the UK the following day using his own legitimate passport - which bears the name Paul Harris.
The court heard that is the name that appears on the EDL leader's passport, although he uses aliases.
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.
Having carefully considered the legal tests and balanced rights to protest against the need to ensure local communities and property are protected, I have given my consent to a ban on all marches in Waltham Forest and three nearby boroughs for a 30-day period.
I know the Metropolitan Police are committed to using their powers to ensure communities and properties are protected.
A series of marches by a right-wing group has been banned amid fears of violence on the streets.
Policing minister Damian Green agreed to the Metropolitan Police request for the ban to stop serious public disorder ahead of marches by the English Defence League in Waltham Forest, north-east London, and three surrounding boroughs.