Johnson grew up in Lilburn and played two seasons for UCF before being selected in the fourth round of the 2010 SuperDraft.
He has played at different levels for U.S. national youth teams, and had made five appearances for the senior team.
If the trade is completed, Johnson will become the second goalkeeper signed by Atlanta United. Alex Tambakis was the first, and also the club’s first announced signing.
Other players signed by Atlanta United include: midfielders Hector Villalba, Junior Burgos, Andrew Carleton, Chris Goslin and Chris McCann, and forwards Kenwyne Jones and Jeffrey Otoo. The club is expected to complete a trade with Philadelphia for midfielder Kevin Kratz when the window opens on Dec. 11. Carleton and Goslin are also Atlanta natives.