I don't see how that could possibly be true. The same flow has to be achieved either way, and lights will always have some margin of inefficiency in switching. Seems lights will always be strictly worse than roundabouts in this sense.
There are also solutions for large vehicles where the center is raised but not impassible.
You over estimate the intelligence of the average American. I've lived in a few cities with a number of roundabouts and while I love them, the number of stupid people that panic and..
-stop in the roundabout
-stop before the roundabout and let their brain buffer for 30 seconds.
-somehow go the wrong way in the roundabout
-fail to yield to traffic in the roundabout
Is way too damn high. It makes traversing one a high stress situation since you have no idea if grandpa grunt and run in to you is about to perform a confusion based terror attack on the traffic control device.
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