The taxes had begun to get a little out of control by the time of the American Revolution, as the British were using them as a way to pay for the French and Indian War. The British were also placing restrictions on who the colonists could trade with as a way to insure that money and goods from the colonies wasn't leaving the British empire. The American colonists weren't used to the British being so actively involved in their lives by this point. Britain had, for the most part, allowed the American colonies to develop and grow on their own up to this point, and many colonists felt like it had been working well that way. The colonists felt like they had been loyal to the empire and deserved to be treated as equals, and when they weren't it made people angry enough to feel like independence was their only option.

As far as being at a great military disadvantage to the British, that is true to some extent. The British were better supplied and had a larger number of trained soldiers at their disposal for sure. It's not like the colonists were completely untrained and inexperienced though. They had just fought along side the British in the French and Indian War and had greatly developed as soldiers there. They were also used to fighting Native Americans, and knew how to fight in their surrounding. This is an advantage that they had on the British, who still used traditional European military tactics that worked well on battle fields, but not so much in wooded areas where they were susceptible to ambushes.