A lot of it has to do with individualism vs community minded mentality like Japan where they have a small fraction of the fatalities as the US. In Japan they follow the rules for vehicles and pedestrians as they put community first. In ths US, it's basically do whatever you want and complacency as far as speeding, phone use, jaywalking, DUI, etc.
For Ebikes and kids, there isn't a strong push to encourage training and mentorship, along with bad parenting. I don't agree with helmet and seatbelt laws, but I think it's stupid not to use one.