It really is so obviously reasonable it makes you wonder why this isn't already in place. For instance e-bikes are all speed and power limited, why aren't cars?
It would take a lot more effort and political will to roll this out to millions of vehicles already on the road than to enforce it on a budding new vehicle category, though. That's pretty much how new safety codes always work.
The US is a hodgepodge of local laws. AFAIK, there is no federal speed limit for e-bikes. The class 1/2/3 designation is optional. And class 3 often conflicts with local laws.