Probably not. I think they probably stuck that on there to just cover their own butts in case you were from some non-EU country that Spain generally doesn't let in (something middle Asian or African, I have no idea what Spain's visa requirements are for non-EU countries). Don't worry about it, since you can obviously enter Spain on your American passport as a visitor! I just came back from there, actually. The border guards couldn't give a toss, as long as you fill in their little white form and show a valid passport.
