Final answer:
The Nonimportation agreements and the Stamp Act Congress were the most effective in inspiring intercolonial unity and contributed to the repeal of the Stamp Act.
Step-by-step explanation:
The most effective factor in inspiring intercolonial unity and contributing to the repeal of the Stamp Act was the Nonimportation agreements. These agreements were a form of economic protest where colonists agreed to stop importing British goods in order to put pressure on the British government to repeal the Act. This unified action among the colonies demonstrated their collective resistance.
Another significant factor was the formation of the Stamp Act Congress, which brought together delegates from nine colonies to discuss their shared grievances against the Act. The Congress issued a Declaration of Rights and Grievances, asserting their opposition to taxation without representation.
While groups like the Sons of Liberty and Daughters of Liberty played important roles in organizing protests and boycotts, the Nonimportation agreements and the Stamp Act Congress had a greater impact in inspiring intercolonial unity and ultimately led to the repeal of the Stamp Act.
Learn more about Factors contributing to intercolonial unity and the repeal of the Stamp Act