Before Pope Francis heads for the U.S. after visiting Cuba, take a second to read about how the United States re-established relations with the Papal States after they lapsed in the 1800s due to anti-Catholic sentiment in the U.S.
Because of the nature of the Holy See, many Americans felt that establishing diplomatic ties with the Vatican would be violating the Constitutional separation of church of state. This made the journey to diplomatic relations difficult.
Read on at the link to learn more!