What if the Arch Duke's car never pulled up in front of a failed assasin triggering World War 1.
An attempt had been made earlier in the day. It failed when a bomb thrown at the Arch Dukes car earlier in the day missed. By complete chance the Duke decided to visit the injured in hospital and his driver took a wrong turn.
The Dukes car ended up stationary, directly opposite the would be assassins co-conspirator who shot him triggering WW1 via a web of protection pacts and complicated diplomacy.
That is the sliding doors moment of all of modern history. Without it there is likely no WW1 or 2.
Britain, France, Russia and Germany would be far more wealthy, the US far less wealthy. Millions of people wouldn't have died.
Also far less advancement in medicine, weaponry, nuclear arms and power. No moon landings. Less advancement in aviation.