Lou Reed barred Susan Boyle from singing his classic “Perfect Day” on last night’s “America’s Got Talent.” Boyle, who became an Internet sensation after appearing on the British version of the show, had been rehearsing Reed’s song with a 100-piece children’s choir. “Lou didn’t want Susan to perform his song, and he’s not a Susan fan,” a source said. “It’s a big deal to change a song at the last minute. Susan was really upset. She was in tears and was forced to pull out of the show, and decided to come back to the UK.” Reps for Reed, Boyle and NBC declined to comment.