That's what I did in my ye olde no AR TL.I'm working on a timeline that includes the American colonies remaining loyal (it's not the actual POD, though) and my current ideas consist of dividing up the 1760 American lands into three new Kingdoms: Virginia, New England (using the Mason-Dixon line if it's not too anachronistic) and Canada. I don't think individual Colonies would be big enough to count as Kingdoms, and counting them as Counties wouldn't make sense when they're themselves made up of counties.
Then further kingdoms appeared out west, IIRC 'Indiana' (not a kingdom but a big united native nation), Columbia and...err....another one.It really was some time back.