The point of divergence of this timeline is quite simple. On the 8th October, 1768, François Claude Marquis de Chauvelin was shot and killed by a random musket ball at the Battle of Borgo during the attempted French invasion of Corsica.
Nevertheless, the ramifications were enormous for European and American history over the following years and decades. Even before the end of the 18th century, events had already diverged from the OTL in the following manner:
- The French rout at Borgo encouraged Great Britain to take a stand against the French invasion. By the end of 1768, faced by the threat of war against its neighbours, France had withdrawn from Corsica and recognised its independence.
- The British government under the ministry of the Duke of Grafton became more popular than ever after this intervention. Lord Grafton was not forced to resign in 1770.
- Unlike his OTL successor, Lord North, Grafton favoured a reconciliatory policy towards the American colonies. Discontent in the colonies was much dampened, and there was little sympathy for dissident organizations such as the Sons of Liberty.
- The First Continental Congress did not order a boycott of British goods. The petition it send to King George III was read and acknowledged by both the King and Lord Grafton, and some concessions were made.
- As a result, the only colonies which revolted in 1775 were Massachusetts, Connecticut and Rhode Island. The rebellion was quickly crushed and its leaders deported to penal colonies in the West Indies. The majority of Americans remained quite content under British rule for the time being.
- Meanwhile in France, the failure of the Corsican expedition had led to the downfall of the duc de Choiseul as Foreign Minister. Without his support, the provincial parlements were weakened and Kings Louis XV and XVI were able to force them to accept royal authority.
- Without a ruinous overseas war to spend money on, French governmental finances were much improved. With the parlements crushed, Louis XVI and Turgot were able to force through their plans for taxation reform, improving finances even further.
- With their main grievance addressed, and without an American role model to inspire them, the Third Estate was able to agree to a compromise with the King. There was no French Revolution in 1789, and no spread of revolutionary spirit across Europe and the New World.
Obviously the exact chain of events that resulted in these immediate outcomes is much more complex. but there's time to fill in the details. Likewise, the continuation of the timeline into the 19th century and beyond has yet to be determined.