It helps that most Catholics in America were Irish & Italian, and were hence suffering thinly-veiled racism. There were a lot of German Catholics as well, but I never recall reading anything about them being perturbed outside of the World Wars, where it was their German identity that was at issue and not their religion. There's a large German Catholic population in Minneapolis-St. Paul who settled from the Rhine area (a Catholic stronghold) so if there was harassment I would have heard about it back in the day.