Catholicism is a very large religion in the US, perhaps the largest. Many Catholics may have formally agreed to be subject to the Pope in their membership within the Church. Without thinking, they have agreed that their government is the Papacy, not the US government. They would never stand against America, however, if the Papacy require them to. But their Church membership agreement makes them appear to be aligned with a foreign government in the eyes of the FBI. Most other religions in the US have a leadership right within the US country, thereby making their religions to be part of the US.