When we visited Sacramento last year, we visited a Wells Fargo museum and we noticed that the stage coach drivers sat on the right of the stage coach. We queried this and the proprietor said this was because they did drive on the left then, but changed over to the right just to be awkward and different from the British - basically just for spite I suppose.
It's all to do with the French Revolution - the established route was ride on the left to have your sword on the right, and this was the same the world over. The bourgoius in France drove their carriages on the right to overtake and avoid the proles. When the revolution came he peasants etc decided they could use the Right hand side of the road out of principle. Hence countries with no French influence such a Japan drive on the left, as per traditonal sword-sword ways.