I don't find driving on the opposite side of the road a problem; what I do find hard to get used to is the location of things in the car.
Most of my driving overseas was done in Australia. So when I had the car, not only was I not used to the licenses down there (they separate them out by type of engine; if you have a manual, you could drive a manual and an automatic; if you had an automatic, you could only drive automatics. Your license would indicate such), but also where what was located where in the car.
I could get used to the gear shifter in the middle between the seats; cars here in the US have had those for a while.. but switching gears in a manual transmission car with your left hand was weird! Second, the windshield wipers were on the left side of the steering column, while the signal indicator and column adjuster was on the right side of the column. I get to a 4-way stop, instinct kicks in, and flip the left switch thinking I'm signaling, and I turn on the wipers instead. 😱 😱
Other than that, it didn't take long to get used to the other side of the road.. in fact, it was easier.
BL.