What is one reason why the English were afraid of a Roman Catholic monarch?

Unpleasant memories of "Bloody" Mary, who had burned Protestants at the stake, remained.

Roman Catholic kings had joined England with Italy.

A Roman Catholic king would eliminate the English language.

Roman Catholics had blown up the Parliament once already.

The English people had feared of the possibility of a Roman Catholic to be a monarch of the British Empire for the main reason that it has the immense power to dictate the parliament in banning the Protestant Religion. It is a common belief that the Brits had not much embraced the Catholicism thus establishing their own church called the Church of England.