In the late 19th into early 20th century Japan, the country wanted trains. Various countries saw a money making opportunity and bid to help Japan build a train system. The British won and so put the trains on the left side. Japanese trams followed suit and then so did the roads. Post WWII, the Japanese island of Okinawa was occupied by the US, and they changed the island to right hand side driving, but the island went back to left hand driving a good time later.
In 1970 Burma changed from driving on the left, the British colonial side, to right hand side of the road. Which side of the road you drive on in many Asian countries can be a bit of theory anyway, rather than practice.
Places like Poland, Canada, Brazil, Portugal and Spain changed to the right in the early 20 century. It amuses me that Austria changed to the right between 1919 and 1938. It took nearly twenty years. That sounds like chaos.
A quote from The Guardian in 2009 when Samoa joined Australia and New Zealand with driving on the left. Car horns and sirens sounded, church bells rang out and roads were crowded with vehicles as Samoa today became the first country in decades officially to switch from right- to left-side driving.
But today, the 3rd of September, 2017, marks the fiftieth anniversary of when Sweden changed from driving on the left hand side of the road to the right hand side. Sadly Sweden's trams did not undergo the change and were replaced by buses.
This rather wonderful photo I believe shows the chaos in a Swedish regional town as motorists adapted to the changed side of the road driving.