There was a programme called Routemasters on Radio 4 this week about white line painters. They gave the impression that Americans started driving on the right after a female doctor started painting lines down the middle of the road after she was becoming fed up with treating casualties after cars hit each other because there weren't any rules about which side to use. You can hear it again from
http://www.bbc.co.uk/radio4/progs/listenagain.shtml#r.