I've driven in left-drive countries and even after "getting used to it", it still made no sense. I start with the assumption that most people are right-handed (the why is not important), so you want the dominant hand to do the precision stuff, ie steering, and the minor had does the clunky stuff, ie changing gears, or having a drink! In left-hand-drive cars the dominant hand is doing the minor stuff.
Sure, we can be trained -we are good monkeys - like training the foot to brake gently. lol.