In a failed American Revolution scenario, for it to be serious, you have to answer 1) What becomes of the revolutionaries? Are the English generous in surrender, or harsh? 2) The slavery question: Does England continue on its course towards abolution, or does the the presence of defeated american mean that England opposes abolition more vigoriously? 3) As a derivative of the slavery question, does England embrace slavery, and thus bind the southern states to it in the long run, or does it oppose it, while allowing off-shore manufacturing the north to grow more powerful?
There is no British wins the AR scenariou, I can imagine, where Britain does not soon become emroiled in the great Slaver Debate.