This is a matter of much debate, but in the last 20 years no one has dethroned Patrick Collinson's thesis that by the 1580s England can generally be seen to be a "Protestant Country". That being said, there were still Catholics of course. 100 years later, after the Glorious Revolution brought toleration for Catholics, more than a handful came out of the woodwork.

"Catholic" merely means "universal". Everyone who went to church (as people were required to do in those days) would have stood to recite a creed that affirmed belief in "the holy catholike church". (This image is from Elizabeth's 1559 Prayer Book). The Church of England still considers itself part of the "Catholic Church".

In the first few centuries, the adjectives used to identify those who followed the pope would typically be "Papist" or "Roman". For example, the Act of Settlement excludes from the throne all and every Person and Persons that then were or afterwards should be reconciled to or shall hold Communion with the See or Church of Rome or should professe the Popish Religion or marry a Papist