The rule is that a US driver's license is valid in Germany for 6 months with no paper work. So tourists need to do nothing. Then, if you are are here longer than that, you can file an extension for another 6 months, giving you 1 full year that a US driver's license is valid.
Getting a driver's license here is a fantastic display of bureaucracy and showcase of German rule making. Not to mention it can cost well over 3000€ and take somewhere around 6+ months. That"s not to mention the mandatory driving classes, the safety instructional classes, or the first aid seminars offered only in German.
Since I would be here for over a year, I was saavy and motivated to avoid the standard process for getting a drivers license.
It"s easy! And you can to!