Answer:
England, Scotland and Ireland.
Step-by-step explanation:
With the death of his cousin Queen Elizabeth I of England, King James VI of Scotland unified the kingdoms of Ireland, Scotland and England which came to be known as the "Union of the Crowns". This even occurred when he ascended to the throne of the monarch, becoming the leader over the three kingdoms unified into one.
Even before the death of the English monarch Elizabeth I, King James of the Scots had always suggested for the unification of the kingdoms under a single ruler. But his suggestions were met with unresponsive approaches, making it uncertain and difficult for it to actually happen. His approach for one monarch over all kingdoms, one parliament to make a single law for everyone in the three kingdoms could only be successful when Elizabeth died leaving the kingdom to him.