I think the USA issue is probably a result that many in our culture are raised in a paradigm where things should be organized and orderly with clear rules, everyone should obey them, and everyone should wait for their turn. Roundabouts, at least at first appearance, are contrary to that mindset.
I think this is a large part of it.
I also think that the problem is a lack of standardization and notification. Frequently the signs for how the roundabout works are JUST in front of the roundabout. If it turns out you are in the wrong lane, you are going who knows where as the locals just shove you along.
All in Indiana.....
I have seen single lane roundabouts, these are pretty easy to use and navigate IMHO.
I have seen double lane roundabouts. These are far more confusing to me in heavy traffic. Sometimes the inner lane continues around and the outer lane comes and goes for each road. Ultimately you have to swerve in and out of lanes as you go around trying to get to your chosen road. I think these are the easier of the 2 lane roundabouts. Sometimes both lanes go all the way around. Which makes even less sense to me. If both lanes wrap around continuously, once you are in the inner lane you would never be able to get out without swerving in front of someone to get to the outer lane. If you are only supposed to be in the outer lane JUST before you pull onto the next road, then most people use the double lane roundabout incorrectly. Usually you have 2 bumper to bumper lanes of traffic getting crammed into the roundabout and with a lot of swerving, honking and jockeying as people try to figure things out.
I see this is how roundabouts are supposed to work, but the "wrong" ways mentioned in this video is how I have seen most people try to use a roundabout in Indiana.
https://www.nhpr.org/post/nh-dot-produces-tutorial-how-navigate-two-lane-roundabouts#stream/0
I have seen a multi lane roundabout (somewhere north of Indy) that was a frigging nightmare. More or less, same problems as above, but with even more lanes it was just that much more chaotic.
The one thing I have learned is USE YOUR TURN SIGNALS AND SLOW DOWN!!!! It helps everyone know where you intend to go even though you may not know how to get there. AND...watch everyone like a hawk. Just assume that the people around you are just as clueless as you possibly could be.
It will probably take several decades to education the masses of Indiana drivers, but we will eventually get there. Until then, be careful, slow down and use your turn signals.