I grew up in Philadelphia, and remember well that most local highway intersections in New Jersey were controlled by traffic circles, AKA roundabouts. Virtually all have been removed, because they were high-accident areas. Not so many, but still some, in PA, too--notorious was the famous "airport circle" about a mile from the Philadelphia airport. It was in a commuter route from the navy yard, south Jersey, and industries along the Delaware river. Evening rush hour EVERY day, there was an accident. It was removed long ago.
I've negotiated the roundabouts in the UK and Ireland, and they seem to work, though. My colleagues in the UK tell me that the high-accident areas there are cross intersections, not roundabouts, but I've never seen any real statistics. I find them pretty cool--if you don't know where you're going, you need not commit to a road. Just do a couple of orbits, read all the signs, and pull out when you've figured it out.
It's been a long time since I drove in France, but at the time, the cars entering the roundabout had the right of way over those already in the roundabout. (Rule in the UK & Ireland is opposite, fortunately.) This was a prescription for gridlock, but in France, that's the natural state of affairs, so no one ever noticed. I was once told that the rule has changed, but I don't know for sure.
We have one here in Long Beach, within the city, on Pacific Coast Highway. I see absolutely no need for it, and it's pretty hair raising to negotiate. When I'm in the bugeye, I avoid it. But it has been around forever, one of the last bits of the old city, so it probably won't be removed until some actor or sports figure gets killed there.