The change is mostly around making rules more strict for cyclists, as cyclists... well, they also pose a danger to pedestrians! There is a pretty famous case of a cyclist hitting an old lady and killing her.
Some people moving here get annoyed because a lot of times the liability split ends up being 90% driver/10% victim, because there are technicalities, but generally speaking even for pretty "egregious" behavior from pedestrians the driver is ultimately expected to be doing their best. Things like "but there was a blind corner, how could I know somebody was going to ride from that corner" hold no water because drivers are supposed to slow down in those cases, for example. I don't know the state of liability in the US but I imagine it's a bit less victim-friendly.
You didn't really answer the questions I was asking OP for either. Japan puts a large onus on drivers but appears to have backed off from some of it? That is actually interesting though, why did they change?