History of the Catholic Church in the United States
The Catholic Church in the United States began in the colonial era, but by the mid-1800s, most of the Spanish, French, and Mexican influences had demographically faded in importance, with Protestant Americans moving west and taking over many formerly Catholic regions. Small Catholic pockets remained in Maryland, Alabama, Florida, and Louisiana, but scarcely anywhere else.
Source: Wikipedia — History of the Catholic Church in the United States (CC BY-SA 4.0)