Somehow it is, and statistics prove it [0]. There a lot more to safety than just physics.
Safety takes into account many other factors, this is why speed limits vary. Driving in Germany is safer than in places with worse infrastructure, general state of the vehicles, or driver education (as in "obeying the rules"). Simply put, better roads, better cars, and more conscious drivers will lead to higher safety even at higher speeds.
Romania and Bulgaria have a whopping ~3 times higher road death rates than Germany despite having low speed limits. This obscures the fact that both countries have a relatively poor general state of the infrastructure, of the vehicles, and of driver behavior.
I'm sure lowering the speed limits would make traffic even safer and also lower pollution, energy consumption, noise, road wear. But thinking safety is an absolute thing is making the same mistake people buying SUVs make.
Germany at least used have an extremely rigorous licensing process so the average German driver was considerably more skilled than the average American. Maybe someone can let us know if that’s still the case.
Still the case, but similar to many other European states. Austria, France, UK and Sweden have the same requirements (lived there or have very close friends on these).
US roads are much easier to drive though. Even in LA driving is much more relaxed. That city is just built for cars. I think it's reasonable that the US driving test isn't as strict.
EDIT: Sweden also has a mandatory snow & ice training as part of the learning. You can do that in Germany, too, but it's not part of your driving exam. Makes, of course, perfect sense given the weather in each of these countries.
German roads are built very well indeed. If you're a US citizen, come to Germany and you'll find like you've travelled 20 years into the future. The tarmac is much better, signs reflect much better, it all feels much better maintained.
Then again, Germany is a tiny country compared to the US. Of course you can build expensive roads if you don't have to build long roads.
By the way, if you drive from Germany to Austria, you'll get that feeling again: they spend even more money per km of highway; it's again a significant step up.
Do you mean in the U.S.? Everywhere? My understanding is that cars in Germany often exceed 100 MPH.