Only the UK (aka "Civilisation") and Ireland and the Channel Islands drive on the left here on the continent.
There was another country (Denmark maybe) which swapped in the 1950s - caused all sorts of problems.
I am right handed, Mrs A can use both hands for most things, A Junior is also right handed. For the first few moments when I drive overseas I have to 'think' where 1st and 5th/6th gears are - close to me or away from me is more influential than left or right. That is of course after the 2 minutes it takes me to stop changing gear with the window winder.
Once moving though normal driving is fine, you adjust. It is intersections or roundabouts that are the real tester - you have to get used to cars going round anti-clockwise instead of clockwise and crossing junctions needs lots of though.
The first time I drove on the right was in the US and spent a week away from roundabouts. Then I came across the only one in SC and it took a good 20-30 seconds to work out what to do.