Wesley was an ordained Anglican minister. He remained loyal to the Anglican church and refused to ordain minsters under the Methodist banner. It was a cause of dissent among Methodists, but I believe he was right.
I believe he was right as well but sadly separating from the Anglican Communion was something that was inevitable due to the American revolution
Rebellion is never a good thing. America could have gained independence righteously. God would have taken care of the UK's intransigence.
Going to war against the crown of England was the very last resort for the colonies and was not an option that was wanted to begin with. The colonial governments tried everything they could to reason with King George III and protest civilly and how did he respond? By sending over thousands of troops to try and silence them. In both American and British history, King George III is remembered as an insane tyrant. When a country is under oppression for so long eventually its citizens are going to push back. Who is to say that God did not take care of the UK's intransigence through the creation of the United States? I agree that Christians should be peacemakers above all else but sometimes just war is necessary and is a biblical concept.
