Portions of The Last King of America: The Misunderstood Reign of George III (Andrew Roberts) are, unfortunately, timely.
The American rebellion surprised the experts:
One of the reasons why British politicians failed to comprehend that Americans would soon be agitating for nationhood was the paradoxical one, considering the propaganda of the independence movement twelve years later, that they were not being persecuted in any discernible way. ‘The colonists were the least oppressed of all peoples then on earth, politically, economically and nationally,’ noted Hans Kohn in his seminal book The Idea of Nationalism in 1944, written when half the world knew genuine oppression. ‘Politically the colonists were infinitely freer than any people on the European continent; they were even freer than Englishmen in Great Britain. The favourable conditions of frontier life had brought Milton’s and Locke’s teachings and English constitutional liberties to faster and fuller fruition in the colonies than in the mother country.’19 Royal governors and colonial assemblies generally ruled Americans with the lightest of touches, and the colonists certainly paid the lightest of taxes in the empire. The average American in 1770 paid a tiny fraction of what his British cousin paid in direct taxes, and crucially all of what he did pay stayed in America.
In the words of Edmund Burke’s biographer, ‘The general belief was that responsible people in the colonies accepted British sovereignty; that the disturbances in America were the work of a small minority of trouble-makers; and that American resistance would collapse if confronted with a show of force. If a war proved necessary, Britain would win it quickly and easily. Not until Appeasement in the 1930s did virtually the entire British establishment get something so important so badly wrong.
The British Army was tasked with domestic policing as well as wars with foreign nations because there was no permanent police force in England until 1829. The number of soldiers was miniscule by modern standards:
In 1775 there were only 48,000 men in the entire British Army, including the 8,000 already stationed in North America, which with its other global commitments would be nothing like enough to subdue the 2.5 million inhabitants of thirteen colonies that stretched over a thousand miles from north to south and several hundred miles inland.
In the summer of 1775, the British Army had 10,000 men already in America (mostly in or around Boston) and Canada, or sailing there; 7,700 in Gibraltar, Minorca and the West Indies; 7,000 in Ireland, which at half its normal peacetime establishment was dangerously low; and the remaining 23,000 in the United Kingdom, the minimum number for defence and domestic control, of whom 1,500 were unfit for duty.
The Cabinet continued to suffer under the delusion that the British Army and Royal Navy that had defeated France (with her population of more than twenty-five million) and Spain (nine million) only a decade earlier, and won a great empire in Canada and India, would, if necessary, similarly destroy the untrained and semi-organized militias of far fewer Americans. The crucial difference was of course that Britain had not needed to invade and occupy France or Spain in order to be victorious in 1763.
What were these professional soldiers up against?
As well as their proficiency with firearms, the Americans also had the advantage of numbers. According to Benjamin Franklin’s calculation in 1766, if a quarter of the remaining male population bore arms, and Loyalists, pacifists and seamen were deducted, about a quarter of a million Americans could theoretically fight against the Crown.
Supplying troops in the field wasn’t any easier then:
The logistical supply problem was immense too: because the local population tended to be hostile – with the American Loyalists providing far fewer troops than the British government had hoped for and expected – food had to be either foraged (that is, requisitioned, with all the local unpopularity that entailed) or bought (routinely at high margins), or else transported 3,000 miles over an ocean that was vulnerable to storms, colonial privateers and, later, enemy navies. Once the British armies penetrated inland, their lack of knowledge of the interior and the inescapable problems of reinforcement and supply both told against them heavily.
I recommend The Last King of America: The Misunderstood Reign of George III, but you might want to skim over some of the exhaustive/exhausting explanations of 18th century English politics (at least as complex as anything we have today and political disputes quite often resulted in violent clashes).