I didn't compare Germany and the USA, I compare the German Autobahn to a specific stretch of 101 in California (for the Autobahn I was thinking of the A9 here but save for the north east most Autobahns are pretty similar).

Comparing on a miles driven basis for the entire country doesn't show the full picture because the miles driven per road type are likely vastly different, traffic density varies extremely in the US but not so much in Germany, and there are 50 different sets of traffic laws and educational requirements across the US.

Given what I've seen here vs. in European countries with good driving test standards, I'm surprised it's not much higher. Maybe the distances in the US are larger? Or perhaps our roads are wider and so have more wiggle room, which compensates for the stunningly bad driver behavior I see every time I drive.

Also, lower top speed limits and higher penalties for speeding.

Which seems like a potentially reasonable policy tradeoff: make it easier for more people to get their licenses, then make it harder for them to kill each other. (NB I would prefer more stringent licensing standards).