Why Do the British Drive on the Left Side of the Road and Americans Drive on the Right Side of the Street?

The British custom of driving on the left was passed down from the Romans.

The chariot driver stayed to the left in order to meet an approaching enemy with his right sword hand.

Americans switched to driving on the right because on covered wagons, the brakes were built on the left, forcing the driver to sit on that same side and, consequently, to drive on the right so they could have a clear view of the road.