What were the key reasons used to justify a revolution against the British sovereign? And what particular historical circumstances are cited?
When King George III started imposing taxes on essential products purchased by the colonists, for example, the Sugar Act, which increases fees on imported sugar and coffee and other items like textiles, they resented it because they did not have representation in Parliament. The battle cry, no taxation without representation is shouted in the colonies.
The Stamp Act, another tax imposed directly on the American colonies which taxes all printed materials. They must contain a stamp which has to be purchased, thus paying the tax. No newspapers, legal papers publications of any kind with the stamp.
The Quartering Act required the colonists to house and feed the British soldiers in their towns.
The colonists battle back and forth with England about repealing these taxes and to a certain degree they are successful. But, in 1767 the British impose a new set of taxes through the Townsend Act.
As tensions build between the British soldiers, the colonists and the English government, we have the Boston Tea Party, destroying a whole shipment of tea, dropped in the harbor. Britain is determined to punish the colonists, especially Boston. England shuts down Boston harbor, until they pay the taxes on the tea.
The rebellion begins to brew fueled by the Sons of Liberty, an organization that had Sam Adams as a member and many others. Resistance to English rule becomes stronger and stronger until it erupts in revolution.