I'm still not sure who's got the right of way e.g. in US parking lots or unsigned back roads. The person going straight, I think? But that's not always clear depending on road topology. "Yield to the right" seems more well-defined, but maybe because I got used to it.
It took me a while to learn to automatically look for European yield signs. It was by far the highest effort to change between the two systems for me.
I don't like the default to yield to progress as it means one is looking for the absence of something most of the time.
Traffic calming is better done with mechanisms not signs.
Incorrect. There are explicit right of way rules for completely unsigned intersections. Yes, they do exist. My neighborhood hasn’t been fully polluted with stop signs yet, so about half our intersections are unsigned. The last crash in the neighborhood that I am aware of was about 10 years ago and was wholly unrelated to intersection control.
Much more interesting are one lane tunnels or bridges that have a yield sign on both sides. Effectively, people just do fist come first served, but if it's at the same time you have to negotiate who has the right of way.