Hilariously, Okinawa was right-lane drive when it was under American administration, but when it got returned to the Japanese in 1972, they also switched the road rules to drive on the left side... except, instead of doing it at, say, midnight, they scheduled the switch to happen at noon.
It was absolute anarchy and for a month afterwards, everyone drove down the middle of the road and switched to one side when someone else was coming from the other direction.
For some reason I hear the Benny Hill theme in my head when trying to picture this situation