To be honest, I heavily dislike Freak on a Leash myself, I just added it for alt-rock variety.
As for La Bamba, if Me Enamora was Devil-Tiered entirely due to being in a different language, I thought that would apply to La Bamba, especially as I think it's tough to sing regardless. But you're right, there's probably tougher stuff there. Can't agree with American Pie, though, it didn't seem that difficult to sing. McLean sings in a pretty simple pitch. But again, it's all subjective. I'll take a second look.