Paris under Anne Hidalgo has been undoing a lot of them because they are so hectic and pedestrian unfriendly.

Place de la Republique: https://www.lejdd.fr/Societe/La-place-de-la-Republique-se-re...

Same in the UK, I find it kind of funny that some North American transport planners are starting to put roundabouts everywhere at the same time as they're being ripped out in London.

They're still pretty much the default junction outside of towns and cities because they do work well but large roundabouts are no fun at all to cycle round

The type of roundabout being installed in America is generally one or two lanes wide, not some of the multilane monsters prevalent in the UK though.

That is an old-style traffic circle, not a roundabout, which is specially designed to improve safety, by requiring cars coming into the circle to approach at an angle, as opposed to 90 degrees, and requiring cars outside the roundabout to yield to cars inside. As someone who's actually driven around the Arc de Triomphe, it's quite dangerous - it is always congested, and has unmarked lanes inside the circle (between 4-5 depending on the whims of the drivers at that particular time). Modern roundabouts are a reaction to dangerous intersections like the Arc de Triomphe.

I've also heard that traffic is so chaotic around the Arc de Triomphe that insurers always assume 50-50 fault for accidents within it.