Young Bart is handed the U2 album The Joshua Tree (1987) in 1985.
In the 1985 scenes, the record store has a poster in the window for the first .38 Special record. This album came out in 1977, and was not a big commercial success at its time of release; its popularity was eclipsed by the band's subsequent releases. Additionally, it was already horribly out of date by the time this scene is set; no record store would be likely to display a poster for an album eight years old that was not commercially successful.
The version of "Hallelujah" the Glee club was singing in 1991 is based on Jeff Buckley's 1994 rendition.
When Bart's mom is driving him to the camp, and Bart puts in U2's The Joshua Tree cassette tape. Then a U2 song starts to play , but the song isn't from The Joshua Tree, instead the song is" Into the Heart" which is a song from their first album Boy.
In one of the first scenes, set in 1985, the record store owner recommended Bart to listen to U2's "The Joshua Tree" cassette. The Joshua Tree was not released until 1987. Later in the movie, Bart had a different U2 tape, Boy, which he asked his mother to play.
Bart tells his Dad that he will be singing at the church and he can listen on AM 1080. Every scene in the movie that shows his Dad's radio shows the band switch in the FM position, not the AM band.
When Bart is in the Camp Lunch Line the Cook Gives him a hot dog with fries, a few seconds later Bart turns around and now has a burger and fries on his plate.