Per capita passenger mileage is 2x lower in Germany vs US[1]; it looks like this accounts for just ~half of the difference - and there are other factors responsible for increased mortality.

[1]: https://frontiergroup.org/resources/fact-file-americans-driv...

Other factors indeed, like population density - I assume you won't like correcting for that.

On the contrary, please show how you would correct for that, ideally with sources.

Why would you assume that?

Only ~1.8x as a function of kms driven. Still significantly better.

https://en.wikipedia.org/wiki/List_of_countries_by_traffic-r...

That's part of the problem.