Presuming the Revolutionary leaders were not killed outright by British troops, they would almost certainly be executed. What's more interesting is the aftermath.
Maybe, especially in high-rebel areas, the British would put Tory administrators in. Is this with a POD before or after Benedict Arnold's defection? If after, he may be set up as a local Governor-General. Diehard American rebels are likely to become terrorists and/or flee beyond the Appalachians.
In a decade or so, the British may be willing to address the grievances of the colonies, but not so soon after putting down a rebellion.
The French Revolution may not happen, or it may be even bloodier than in OTL.
GB's American holdings will probably extend at least to the Mississippi, and include most of OTL Canada, plus the Oregon Territory as a later possession. Whether or not they would seize territory from Louisiana and Mexico remains to be seen.