The Stamp Act of 1765 was one of the major reasons for the American Revolution. The major reason for its controversy was the difference between the mentalities of people living in America and the people living in Britain.
America was colonized by the British by the late 1600s. Naturally, the people who settled in the colonies wanted to be treated as normal British citizens. By the 1750s the American colonists’ attitudes had changed. They believed they deserved autonomy in their matters and would be okay with a little regulatory oversight from Britain. There was also a constant disapproval of British policies and there was a common anger among everyone that no American colonist was in the British parliament to voice their issues. Most of all, they wanted the same treatment as British citizens since they actually were British citizens.
The British attitude, on the other hand, was of a conservative nature. They believed that a colony was supposed to be below the empire and its only purpose was to reap profits for the empire. They were, in fact, planning to stricten the regulations of trade and increase profits. The politicians of the time demanded the same.
This is where the Stamp Act comes in. The British were looking for a way to maximize their profits and introduced a law through which any piece of paper(newspaper, magazine, cigarette wrapping, legal documents, playing cards etc) used in the colonies would be exclusively manufactured in Britain bearing a stamp of the government and this paper would be taxed in all American states.
They made this tax look like funds for the British troops stationed in American colonies. This created a massive uproar and the colonists believed that they were not being treated as British citizens. There were protests everywhere, stamp duty officials were harassed and merchants declared an embargo on British goods. This act was repealed in 1766 though the damage had already been done.
I have also written an answer for the following question:
In 1765, the British government enacted and enforced the Stamp Act of 1765. Many colonists in America were already angry with the British for their other taxes. This tax was especially difficult because the taxes were used for the British military that were located in America.
the colonists were having to pay more for paper goods in order to keep the British military in America who they did not want there. It was controversial because the colonists were opposed to taxing without representation.
Therefore, the British government was forcing them to pay taxes and then pay taxes for the British military to be in America in which they wanted them gone. Unfortunately, eleven years later, the colonists would declare their freedom and go to war.