One aspect of the American Revolution that most people don't get is that, for at least the first year and a half of the fighting, the people who wanted to separate from Great Britain were a small minority. It's hard to estimate such things, but a common guesstimate among historians is that in late 1776, when the British were driving Washington's army from New York, about 10% of the population favored the Revolution, about 10% were loyalists who opposed it, and the other 80% didn't care. To them, ideas like the fundamental rights of man, no taxation without representation, the evils of monarchy, etc. were far less important than the big questions of life, such as, "will my wife live through her next pregnancy?" Or "will my crops come in well enough this year for me to keep my farm?" Or "will the smallpox epidemic wipe out my entire town?" (The Revolutionary War was fought during a smallpox epidemic.)
From the British perspective there was plenty of provocation for what they did. American colonists had attacked a force of His Majesty's soldiers and marines in the performance of their duty, had destroyed several tons of valuable property of the East India Company, had driven a royal governor out of Massachusetts by setting fire to his house and threatening his family, and placed a sizeable force of soldiers and loyal civilians under siege (in Boston).
When the Second Continental Congress met in May of 1775, just after the shooting started at Lexington and Concord, the first thing it did was to issue two documents, the Declaration of Causes of Taking Up Arms and the Olive Branch Petition, both of which said the same thing: the colonists were loyal subjects of King George, they were just trying to make the British recognize their rights as British subjects, the British Army was breaking the law, and they hoped the king would get rid of his treasonous ministers and other officials and stop the war. Of the 55 or so men in the Continental Congress, only about a dozen wanted to leave the British Empire.
During the next 14 months those dozen guys managed to draw enough of the other representatives into their camp to get the Declaration of Independence passed.
When Admiral Howe and General Howe arrived in North America, in the summer of 1776, they bore commissions not only as commanders-in-chief of the navy and army, but as commissioners of the peace. They were authorized to grant the Continenal Congress any terms it demanded, with one exception. The colonies were offered representation in Parliament, the repeal of the taxes they found so objectionable (which really didn't amount to much), and virtually everything else they wanted. The exception: independence. When the Howe brothers arrived, the Congress had just issued the Declaration of Independence, so they refused to negotiate. The rest is history.
Oh - and the colonial militias were not the only non-British military institutions in the colonies. Modern historians have recognized that the colonial military system had three layers: The British Army, the militia, and a group of "semi-pro" regiments raised by the individual states to function as trained, paid, professional fighting men. George Washington commanded such a unit, the First Virginia Regiment, in the French and Indian War. He claimed his troops were as well trained, equipped, and disciplined as most of the British units - and he was probably right. In any case, the story of the war being won by irregular militiamen firing rifles from behind trees at lines of idiots in red coats is about 90% myth.
End of lecture. Sorry; I've been teaching and writing about this stuff for about 40 years, and when the subject comes up I tend to run off at the mouth - or in this case keyboard.