Final answer:
The Presbyterian Scots threatened to rebel because their desire for a Presbyterian church free of Catholic influence was not met, and religious uniformity was imposed by the monarchs, firstly Elizabeth I and later under the Stuart dynasty.
Step-by-step explanation:
The Presbyterian Scots threatened to rebel during the reigns of Elizabeth I and later during the Stuart monarchs because of the imposition of religious conformity and perceived threats to their own religious practices. During Elizabeth's time, tensions arose due to her moderate religious stance compared to her cousin Mary, Queen of Scots, who was a strict Catholic aiming to unite England and Scotland under Catholic rule. In the Stuart period, particularly under King James I who succeeded to the English throne, the Presbyterian Scots and English Puritans were disappointed by James's refusal to remove Catholic practices from the Church of England. They felt betrayed since James had been the leader of a country whose official religion was Presbyterianism, which aligned with their Calvinist theology. The threaten of rebellion was a consequence of the failure to address the grievances of Presbyterian Scots regarding religious uniformity enforced by the monarchs, which contrasted with their desire for a church free of Catholic influence.