What effect (if any) did American propaganda have on the American Revolutionary War?

Certainly from the British perspective, propaganda spread by rebellious colonists, especially groups like the Sons of Liberty in Boston, had a significant impact in convincing colonists to think of themselves as Americans rather than as British subjects and to believe they were being oppressed by the British government. These beliefs were the foundation for the colonists' willingness to take up arms against their former countrymen.
Much of the tension between the two sides in the years leading up to Revolution was due to financial issues; the British government was heavily in debt as a result of years of war with France in both Europe and America. The British believed the colonists should share in the costs of protecting the colonists from the French and Indians and sought to collect from the colonists through taxes like the Stamp Act and taxes on sugar and tea.
The Sons of Liberty and other American writers were able to portray this fairly reasonable request from the British as absolute tyranny and oppression, using slogans such as "taxation without representation is tyranny" and "give me liberty or give me death." The rebellious feelings this propaganda stirred up let to incidents like the Boston Massacre, where British soldiers were attacked by a mob and the Boston Tea Party, where mobs boarded British ships and destroyed property. The British response, a blockade of Boston and quartering of troops there, would lead directly to the outbreak of hostilities at Lexington and Concord that began the American Revolution.