This is not actually that true. Germany is 7x as dense as the US, but Germany is only 5.9x as dense as the contiguous US.

About a third of the contiguous US has almost no people relative to the rest except for a few population centers (Intermountain West and Great Plains). There are several states with population densities higher than Germany, and quite a few within a factor of three, and naturally those will tend to have more people than the others.

So I'm not sure the median surrounding population density for an individual in the US would be that much different from Germany -- I'd think cultural factors, including public transportation availability, would have at least as much an effect on average distances driven.

I'm not sure how relevant "regularly" is if you want to replace someones only car (multi-car households are a different story, but also a large limitation of the market). Yes, for most people you could cover 90-98% of their days with 100 km range, but nobody wants to rent a car just because they have a 600+ km trip planned. It still needs to be able to do that distance with not too many charging stops.