I can imagine that some authorities might find it suspicious, but in OPs case, it is necessary to travel with both passports to have the least hassle.
Entering the US with your German passport or returning to Germany with your US passport if you have both will lead to a lot of questions as you won't have the necessary visa in those passports.
Edit: Although I wouldn't present both passports at the same time, only the one that is applicable or more convenient for wherever you are.
archive.is funktioniert bei mir auch nie, archive.ph aber wunderbar. Hier der Link: https://archive.ph/PRA7k
Leider greift die Paywall da auch.
Edit: Die Paywall ist nur optisch, man kann den Text einfach kopieren.