If US drivers can't handle a roundabout and the odd pedestrian then they shouldn't be driving anyway
If it was a X-roads with only traffic lights or stop signs, would you walk across the Middle of the junction?
In a conventional perpendicular intersection, you can look each way, wait for your turn, and make your way across.
This is true for vehicles and pedestrians alike.
With cars coming and going at random times in random directions, you are looking around and moving around every which way for several seconds, or more, weaving your path into everyone else's, and any interruption of that complex flow pattern is problematic.
There is no place for a slow-moving walker in that, although a cyclist has a reasonable chance.