I just had a special meal on a flight from TXL to EWR and I'm pretty sure that the entree portion for the first meal came from the US, although the other parts must have been local (fresh fruit) and the sandwich for the second meal was definitely made in Germany given the ingredients & style.

That said, I've had trouble getting special meals added to my itinerary online and have found I have to call CO to get it added when I wanted in many cases.