For the Americans who were motivated to rebellion by tax policy (and we perhaps shouldn't oversell this number), the problem was less the amount of new taxes and more about how those taxes were formulated. In the century preceding the American Revolution, Parliament had become the central institution of British government. More importantly, the idea of parliamentary representation lay at the center of British (and American) political thought. Parliamentary representation tied the government to the will of the people, and thus gave the government the power to impose taxes. The American colonies, of course, had no representation in Parliament. Thus, any tax imposed by Parliament on the American colonies internally - as opposed to previous efforts which only collected duties on goods coming and going to America - broke this sacred connection between representation and taxation. This made the taxes, at the very least, unconstitutional (in the sense that they violated the foundation of the British government).

An even less charitable reading of Parliament's actions feed into a popular (conspiracy?) theory of the time: that there was a plot by members of the British government to reduce the American colonies to a state of abject servitude or slavery. If the imperial government could interfere with property - in the form of taxation - then there was nothing it could not authorize itself to do. This fed into widespread fears among Enlightenment intellectual that the nature of any powerful government was to seek greater and greater power until it achieved absolute despotism. Parliament's increasingly militant responses to American protests, particularly the disbanding of Massachusetts' legislature and putting Boston under martial law, played directly into these fears. Those inclined towards this theory quickly came to believe that only a spirited defense from a free citizenry could resist the impending death of liberty.

Other concerns were more practical. Few people in the American colonies has sizable reserves of hard currency; the economy largely ran on the exchange of goods, services, and bills of debt. Most of the new taxes had to be paid in specie at the time of purchase, limiting Americans' ability to by British goods even if they could otherwise afford them. American society in the 18th century was replete with conspicuous consumerism. Buying and boldly using, wearing, or displaying British goods is how Americans broadcast to the world that, even though they lived on the fringe of the British empire, they were truly British. Conspicuous consumption also helped delineate class differences - people of the upper and middling sorts dressed themselves and their houses differently than those of the poor. Interfering with the British luxury market was a direct attack on the sense of the self of many Americans, even those that could not read the radical political tracts of the Enlightenment.

I don't think there was anyone one cause of the American Revolution, but these factors, individually or collectively, mattered to enough people that it got the ball rolling on a bigger, more radical change to come.

Sources

Bernard Bailyn, The Ideological Origins of the Revolution

Jack P. Greene, The Constitutional Origins of the American Revolution

T.H. Breen, The Marketplace of Revolution.