Factual error: The scene where Johnny is walking home from June's house at dusk. If you look at the phone pole as the camera pans you will see cable TV equipment which certainly wasn't around at that time.
Factual error: When the song "Walk the Line" is first being played in the studio during the montage, the guitar player hits a high note on the E string (the thick top string). His fingers were not low enough to play that high of a note on the E string.
Factual error: In the scene of Johnny's first audition, the record producer is sitting at a table telling Johnny he wasn't believable as a God fearing man. On the table is a pack of cigarettes with a bar code on it. Bar codes weren't in use until 1974.