This delay is coverd by Regulation EU 261 and you are entitled to be compensated. You were also entitled to accommodatiion, a free phone call and meals. The fact that your flight originated in the US does not exempt you, if your destination was in the EU and you flew on an EU based carrier. As both these criteria apply to you, you were entitled to the rights bestowed by this regulation.
Write to Air Berlin demanding your entitlement to compensation under EU 261. Copy this letter to the competent authority in Germany. You can write to them in English and they will respond in English. The address of the competent authority is:
Luftfahrt-Bundesamt (LBA)
DE - 38144 Braunschweig
Tel.: +49 531 - 2355115 (mo-th 9-16, fr 9-15)
Fax: +49 531 - 2355707
fluggastrechte@lba.de http://www.lba.de
If you google EU261, you will find copies of the regulations. At the minimum you are entitled to your hotel costs, meals and the fixed compensation amount.
This is the actual regulation, but you can find a summary through google.
http://eur-lex.europa.eu/LexUriServ/...01:0007:EN:PDF