As an American, I detest roundabouts. I've never encountered one with a light before.
There are lots of stoplights that should also be replaced by roundabouts. A solid line of traffic flows right through a roundabout, and most of it is delayed by a stoplight.
The only problem with roundabouts in USA is the 30% of drivers who don't know how to use them, and stop when they see the yield sign... don't be that driver.
But as I said in an earlier comment, the reason they kind of suck in the US is we don't seem to do them right.
* A very wide circle (350ft/100m minimum) with 3 lanes
* Each entrance and exit has 2 lanes.
* The outside lane of the circle directly connects the outside entrance with the "first" exit.
* The middle lane of the circle and the inside lane of the entrance allows you to exit at ANY of the exits
* The far inside lane of the circle exits nowhere without a lane change, but allows you to bypass an exit that might be backed up due to traffic.