If cooler heads had prevailed in Britain, then a permanent separation could have been avoided even after the start of the war. The Americans had alot of friends in the British Parliament, and powerful ones, at that, including no less than Pitt the Elder. However, those voices who saw the American Rebellion as nothing less than a direct challenge to British authority by lowly, ungrateful, hicks who didn't like paying taxes were backed by the king, and after Pitt's death pretty well ruled the day.
That goes a bit too far.
King and parliament treated American colonists more as overindulged Whigs. Even if George III held a personal animosity towards the colonists, Parliament treated them leniently. Even the Revolution after it was begun was negotiable.
The real question would be how the Revolution would have turned out if Parliament saw the colonists in the same light as they saw the Irish during the Jacobite rebellions.
