The main idea or message of "Join or Die" is to encourage the colonists to unite together against the British rule due to the increasing taxations. The intended audience is the colonists.
The dragon in the recycled version is the United Kingdom, which was seen as a tyrant trying to oppress the colonies. The dragon represents the monarchy and the British government, which is trying to control the American colonies through its taxes. The message, "Join or Die," is urging the colonists to unite and fight against the British rule.