Welcome to the forum! Yes there are detectorist in Germany....as far as Americans, I know there is atleast one there....we have a group in grafenwoehr area. I pcs'd down to Italy but I still maintain contact with them and I get to Germany quite often for Family trips and detect while there........I can also put you in touch with a German detectorist in the Frankfurt area.
I'm not there yet but will be arriving in November. I'll be in the Ramstein/k-town area. I'm new to md'ing but I'm looking forward to doing some treasure hunting in Germany.
Just left Germany this past February... LOTS of great hunting there. There seems to be a lot of Roman coming out of the k-town area. I was in the east, lots of old silver, such as the one in my picture, but no Roman stuff. Good luck and happy hunting.
There is some great detecting in that area. a LOT of Roman. I was there and detected for about an hour with 2 guys and they both found Roman coins....I left empty handed. But none the less had a great time.