Final answer:
Charles' foreign policy caused instability in England due to factors such as the Treaty of Dover, his inability to work with Parliaments, and his failure to reassure the English people.
Step-by-step explanation:
Charles' foreign policy caused instability in England due to several factors. Firstly, his secret Treaty of Dover with Louis XIV of France, in which England would join France in war against Holland and Charles would publicly convert to Catholicism, caused anti-Catholic sentiment and fervor among the English people. This led to widespread unrest and division within the country.
Secondly, Charles' inability to work with Parliaments resulted in fiscal chaos and a lack of effective governance. He called no Parliaments and his autocratic rule further alienated the nonconformists, who were being persecuted.
Lastly, Charles' failure to reassure the English people of his determination to defend their traditional religion and civil liberties, and his overall poor leadership, contributed to England's decline as a leader in European affairs and increased divisions within the country.