Roundabouts are a wonderful invention. Traffic generally flows on and off without too much hassle. You wait for a gap in traffic, the hop on, and hop off at your required exit.
Here in America, they've taken that notion and ruined it by turning roundabouts into 4-way stops - sort of like traffic lights on roundabouts in England but without the lights. So rather than flowing traffic, like they're supposed to, they stop traffic. Worse, if the roundabout is big enough, rather than giving way to traffic already on the roundabout like everywhere else in the world, you have to give way to traffic entering the roundabout.
It does rather explain the following comment I saw once:
Watching Americans trying to negotiate a roundabout in England is an entertaining and embarrassing representation of the human ignorance about an intersection that does not require you to stop but does require you to yield. It seems to cause some sort of severe psychological disorder since it is neither green nor red, but requires them to steer and calculate approaching distances at the same time.