It seems, you did not understand my previous posting, so I will try it again:
The "Standesamt" does not know to which religion you belong. The "Standesamt" is responsible just for people living in Germany. As you have been living in the United States, the Standesamt has no idea to which religion you might belong at the moment.
Moreover, even if you would be living in Germany, the "Standesamt" cannot tell you, to which religion you are belonging. The Bethel does not provide "Standesamt" with a list of JWs. Legally, membership in a church is your personal decision, not the Standesamt's decision. Standesamt is just responsible to guarantee that a church respects the decision of its member to leave the church.
So I does not make any sense for you to send a letter to "Standesamt":
- you left Germany already, and are therefore no member of "JWs in Germany"
- you DAed in USA, so you are not a member of JWs in the USA or in any other country
- you cannot delete your church membership ex post facto from historical documents at Standesamt (if any such documents would exist; I strongly doubt it).