Because of the French and Indian War, which was fought on American soil, Britain felt it was only right that the colonists foot some of the bill for the war that was fought to protect them.
Once Britain decided to impose taxes on the colonies to collect some revenue to pay the war bill, the colonists attitude toward Britain changed. They began to feel that they were being persecuted, being held responsible to pay for a war that Britain would have waged anyway, since they were fighting France for territory in North America.