The practice is believed to date back to ancient Rome. Romans steered their carts and chariots with the left hand, to free up the right so they could use weapons to defend against enemy attacks.
This carried over into medieval Europe and in 1773, the British government passed measures to make left-hand traffic the law. But postrevolution France favored the right.
Napoleon was left-handed, and riding on the right proved to be an intimidating military tactic. Britain and France brought their driving styles to their respective colonies. That’s why many former British territories are among the few modern left-hand-traffic countries.
In the US, right-hand traffic goes back to the 18th century. Freight wagons were pulled by teams of horses. and the drivers rode on the left rear horse, using their right hand to more easily control the team. Traffic shifted to the right so drivers could easily avoid collisions.
But NONE of that explains why MSFS seems to have so many Vehicles incorrect !!