> Maybe the US should create separate standards for city streets and roads with low speed limits, that could be a good way to bring down vehicle sizes.

They already have!

https://en.m.wikipedia.org/wiki/Low-speed_vehicle

https://en.m.wikipedia.org/wiki/Neighborhood_Electric_Vehicl...

But it’s a hard sell when the US has so many high speed roads. I mostly see them used for facility maintenance, parking enforcement etc.