驻美国使馆的要求是：Just ask your friends/relatives to send you an informal invitation. Name, address and a copy of the friend's/relative's passport. . A copy of the residence permit is an additional requirement if your friend/relative in Germany is not a German national. If your friends/relatives pay for your travel expenses you will need to submit an official affidavit of support (Verpflichtungserklaerung).
