Can you expand on how the switch relates to not being conquered by Napolean? Was part of Napoleanic colonialism the implementation of left side roadways? I'm not sure how I would Google that and am interested.
From this wiki article... Maybe this has something to do with it!In Continental Europe, driving on the right is associated with France and Napoleon Bonaparte. During the French Revolution, a decree of 1792 created a uniform traffic law, requiring traffic to keep to the "common" right. A little later, Napoleon consolidated this position by ordering the military to stay on the right side, even when out of the country, so that everyone who met the French army had to concede the way. In the early 19th century, those countries occupied by or allied to Napoleon – the Netherlands, Switzerland, Germany, Italy, Poland, Spain – adopted right-hand traffic. Britain, Sweden, Austria-Hungary and Portugal continued or adopted left-hand traffic.
If I remember correctly it was french army ettiquet to ride on one side because of how they carried weapons back then and because of that the armies in conquered territories had to switch. Or something like that.