Anti-Catholicism in America has gradually decreased since the founding of our Republic. At the beginning, anti-Catholicism in America was at it’s height. The newly arrived British colonists were strong believers (as were most British) in the Protestant/Anglican reformation and viewed Catholicism very negatively. This possibly explains why most Catholics settled in one Catholic-friendly colony: Maryland. Amongst Puritans and Congregationalists, anti-Catholicism was heightened by their hatred of Anglicanism, which persecuted both groups and carries many of the same practices of Catholicism. Discrimination against Catholics in the colonies was fierce and common. If some historians are to be believed, laws against Catholics and death penalties for “heresy” wasn’t uncommon.
During the 1800’s, Catholic discrimination was the same heightened state. “Nativism” opposed Catholicism on the grounds that it was “foreign” to the continent, as opposed to the “Native” protestantism. Immigrating Irish Catholics were blamed for violence and drunkenness. During this period, however, not much is known if the colonies still actively executed Catholics for heresy.
The 1900’s saw the rise of the Racist Ku Klux Klan. The Ku Klux Klan could be seen as nativist as well, since it was in support of only the British style Protestantism and was against the “papists.” The Ku Klux Klan harassed Catholics, though I’m not sure if they actively targeted them for death as they did the black Americans. Al Smith became one of the first Catholics to gain a major nomination for President, which shows that the colonial anti-catholic sentiment was slowly becoming a idea of the past. Only the Ku Klux Klan actively opposed Catholicism, though anti-catholic sentiment was still in America…as seen in the 1960 election. In the 1960 election, John F. Kennedy was opposed by many Protestants. They viewed him as being a sock-puppet for the Bishop of Rome and that he would have the Pope on speed-dial at all times. After Kennedy’s election, anti-catholic sentiment slowly dissolved as the Ku Klux Klan lost power and Kennedy proved himself to be loyal to the Republic and not the Papacy.
The late 1900’s saw a rise in Catholic politicians and even in current days, Catholics hold many elected positions from city, state, and federal government positions. The current speaker of the house is Catholic, and Vice President Joe Biden is Catholic. Many senators and Representatives are Catholic – the strongest religious majority in congress is Catholicism, if I correctly remember.
These days, anti-Catholicism is still present but is fairly weak compared to the fact that Catholics used to be seen as second class citizens who were loyal only to the Bishop of Rome and were heretical.
For this reason, I would say that anti-Catholicism has gone down gradually, but drastically, over American history. Recent clergy abuses of children has increased anti-catholicism somewhat but not so much to the point that Catholics are targeted for hate killings.