It wasn't part of my driving test in Virginia, at least when I took it. I'm guessing if your state has a low number of roundabouts [0] then it's pretty unlikely you'll be tested on it. I'd be interested to hear if Marylanders (#1 in roundabouts:intersections) have it on their test.
Personally, I freak out when I see a roundabout coming up, and slow down dramatically. Or, I completely avoid them.
[0] https://www.citylab.com/transportation/2016/03/america-traff...
It's possible that even when slowing down the roundabout still ends up being more efficient, since you don't have as much "stop/go" action going on
This is generally how it works in the UK, except for newbies who tend to always stop completely rather than try to time the merge where possible... I've heard that this is actually taught in advanced driving in the UK (to maintain flow when possible, time merges etc). Frankly there are some roundabouts in cities at rush hour which are frightening for new drivers and you just can't join unless you have good timing and can get up to speed quickly (or get a lucky smooth merge).
This is exactly the question asked by myth busters.
You can see the segment here[0]
They measured throughput for both 4-way stops and roundabouts, with both people who hadn’t used them before and people who had.
Unsurprisingly (for me at least) roundabouts were significantly better, even for people unfamiliar with them.
0: https://m.wimp.com/mythbusters-four-way-stop-vs-roundabout/
Roundabouts are not part of the driving test in DC. Indeed, roundabouts are so scary to Americans that most of the ones in DC have traffic lights. We also have roundabouts with roads cutting across them: https://ddot.dc.gov/sites/default/files/dc/sites/ddot/ward%2....
hah, that is completely insane! the design completely looses all the benefits of it being a roundabout. Even those crazy triple mini roundabouts make more sense than that one.
I actually find roundabouts easier to navigate than large crossroads, I think this is partly because they actually are objectively easier and safer to navigate (one stream of traffic) and partly (but mostly) because they are dominant in the UK.
But for the same reason (familiarity) I expect many in the US would find roundabouts hard to navigate (and maybe unsafe as a result?), it's more about what you are used to and what you had to learn as part of your driving test.
Are roundabouts part of driving tests in the US?