What was the long-term impact of the Stamp Act of 1766?

The British Government, deeply in debt and financially strapped for cash from the Seven Year's War, turned to the American colonists to recoup some the funds they invested. The government imposed a tax or fee attached to every document and printed piece of paper to be paid to the British government. The list of items taxed included everything from ship's papers, legal documents, licenses, newspapers, books, miscellaneous publications, and playing cards—virtually any item made of paper!
The Stamp Act of 1765, as it became known, was one of the earliest in a series of taxes and fees imposed on colonial citizens. An unbiased observer might conclude, considering the amount of money the British invested in the American colonies (including providing military defense), that the tax would not have been considered unreasonable. That was not the case, as the American colonists immediately protested the tax and took steps to circumvent the collections of fees.
Although every American colony under British control had promised to support the British government in exchange for land grants and financial and military assistance, the colonists vehemently objected to the tax. In some cases, violent protests, including attacks on the tax collectors, occurred. The colonists argued that only the American colonial governments could impose taxes on the American colonists and that the British had overstepped their legal authority. The British countered the colonists were funded and supported by the British government. Many of the colonists had signed loyalty oaths with the British in exchange for passage to America. In the land grants and charters of the colonies was the language that required the colonies to be loyal to the British crown and remain loyal as citizens of Great Britain. As a territory of the British, the government had the legal authority to impose taxes and fees on every citizen.
The long-term impact of the Stamp Act as examined by historians is the tax provided fuel to the fire—if not for complete independence from Great Britain, then for an improved relationship that placed the interest of the American colonists on the same level footing as that of the British Government. The financial cost of the tax was not the only element of the Stamp Act in 1765 the colonists disagreed. There were provisions in the legislation that denied colonists a right to a jury trial if they were accused of not paying the tax. Denying jury trials for the accused agitated the colonists probably as much as the tax.
The colonists were told the tax was necessary so that the British military could continue their role protecting the colonists. American colonists openly complained about the British army and their cavalier treatment of the rights of the colonists. Some colonists questioned why British troops remained on the American continent years after the French had left, when colonial militias had proven effective in defending colonists from threats from hostile Native American tribes or potential threats from foreign powers. These complaints later made their way into the Declaration of Independence. In that regard, some historians argue the Stamp Act of 1765 was the precursor to calls for independence, the Declaration of Independence, and the American Revolution.
Although the tax was repealed in 1766, the British continued to maintain they had the authority to impose taxes without the input of American colonists. The Stamp Act of 1765 and other similar taxes hastened the inevitable split between the American colonists and the British government, leading to the founding of a new nation.
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