I landed in Geneva after an 8 hour flight, got in a rental car, and did roundabouts. Never had even heard of one before. It's not hard. But then, I'm not dumb. But you're right, it's just not the way we do it. And in much of the country, the freeway system sort of replaces the need for them.
I also landed in London, got in a rental car, and drove on the wrong side of the road. That was a blast.