You need to read "The War For America" by Piers Mackesy. Definitely from a British point of view but gives some great insight to the internal political happenings and the global aspect of the war. He and others have postulated that the war in America was a side-show in what was the real first "world" war. The English were engaged here in what became the States, the Caribbean, the Mediterannean and India with the French, Spanish and others. This was the war in which the English captured Gibraltar. Kind of a continuation of the on-going conflicts between the English, French, Spanish and other empires.
Remember most "Americans" and "Englishmen" though of the colonies and inhabitants as "Englishmen" and loyal to the Crown and they were for the most part up until there was a ruling party change in England and the new government made a series of blunders that led to the fractures. Did the French join out of altruism? NO, they wanted to win back some of the losses they incurred in previous conflicts.
Part of the reason that the Brits didn't squash the revolt like a bug was they were spread too thin in other areas and they didn't recognize the full import of the discontent. Both in the US and UK at the time, hence the use of Hessian and other mercenaries, they didn't have the troops available and couldn't raise enough in England to fight against family.