What evidence was there that colonists acted in a unified fashion before the passage of the Declaration of Independence?

Before te French and Indian War, the individual colonies viewed themselves as separate entities only connected by their common heritage and their loyalty to the British King. When the acts of Parliament began to strip individual colonies of their rights and self-rule, other colonies noticed. As soon as the Stamp Act was passed in 1765, colonists began to organize a unified protest. Nine of the 13 colonies met to discuss the Stamp Act and resolved that the colonists, as British citizens, had the same rights as citizens living in England. Furthermore, they established the idea that it was unlawful for Parliament to impose a tax on the colonies, because the colonies had no representation in Parliament. Five years later in 1772, Samuel Adams began the Committees of Correspondence in order to strengthen the idea that an attack on one colony represented an attack on all of the colonies.