Johnson was born in Canada, but moved shortly afterwards to England where he started playing soccer, attending the Merchant Taylors' School in Crosby, near Liverpool.

When he was 10 his family once again moved, this time to Woodridge, Illinois, and he played youth soccer for the Sockers FC Chicago.

While back training in Heerenveen for preseason, MLS team Real Salt Lake offered Johnson a contract, which he accepted.

He started and played 45 minutes for Real Salt Lake in the 2009 MLS Cup final against the Los Angeles Galaxy despite a bout with food poisoning, with his side ultimately winning in a penalty shootout.

[9] In December 2015, Johnson was traded to Toronto FC in exchange for a conditional second-round pick in the 2017 MLS SuperDraft and targeted allocation money.

[12] In scoring that goal, Johnson collided with Whitecaps goalkeeper David Ousted, resulting in a tibial plateau fracture of his left leg.

[16] On May 2, 2021, Johnson made a return to soccer, signing as a player and player-mentor with developmental NPSL team Central Florida Panthers.

He has so far represented Canada in two FIFA Tournaments[18] Johnson provided the assist to André Hainault winning goal against Belarus on March 29, 2011.

[24] After almost two years since his last call-up, during which he dealt with illness, injuries, and personal commitments, Johnson was recalled to the national team by Canada coach Benito Floro for 2018 FIFA World Cup qualification matches against Dominica on June 2, 2015.

[26] Johnson's grandfather is Brian Birch, who had a successful career with Bolton Wanderers, including an FA Cup winners medal in 1958.

[28] On September 6, 2017, Johnson was arrested on a domestic battery charge against his wife, and suspended from the team while the incident was being investigated by both local police and the league.