Final answer:
Catholic 'Americanists' supported separation of Church and State, religious liberty, and American democracy, but not Papal Infallibility.
Step-by-step explanation:
The Catholic clergymen who took up the name "Americanists" supported ideals such as separation of Church and State, religious liberty, and American democracy. However, they did not support the idea of Papal Infallibility, which is the belief that the Pope is incapable of error in pronouncing dogma. Therefore, the correct answer to the question is D) Papal Infallibility. Historically, Americanism was a term used to describe a group of related views among American Catholics who aimed to adapt the church to modern civilization, and papal infallibility was seen by some to conflict with American principles such as freedom of conscience and separation of church and state.