Aufgrund der Streiks bei Lufthansa im Dezember 2016 wurden für Sendungen in die USA Ableitungen über alternative Transportrouten notwendig. Unter anderem über den Seeweg. Das führt aktuell noch zu stärkeren Verzögerungen bei der Zustellung von Economy Paketen in die USA.
Translation:
Due to a strike at Lufthansa in december 2016 packages with destination USA need to be redirected using alternate transport routes, amongst other by ship. This results in even bigger delays delivering economy packets into USA.
Source: https://www.dhl.de/de/privatkunden/pakete-versenden/weltweit...
If you have the DHL tracking number you should try tracking.
There's also the DHL facebook page where you can start a facebook chat, with good luck your supporter will speak english. (Just try!) https://www.facebook.com/DHLPaket/app/1609168226005546/
From what it looks there's a high chance your package is on a ship somewhere. And even more importantly, the sender should create a "Nachforschungsauftrag" with DHL (ha, one of our bureaucratic german words I can't even find a translation for - it's a request for inquiry of a lost package). Even with domestic packages over here the tracking information sometimes is plain wrong, and I expect it even more so to be wrong if they don't use their usual ways of transport. (No tracking of all those packages in a shipping container on a freighter.)
Good luck. (Btw, once I have given up on a package from the US to Germany after 6 months. The day after I gave up and purchased an alternative product my packet arrived ... UGH).