From what I have been able to find, it seems the first 3 characters of the VIN don't indicate production location. Based on this the first 3 is just the WMI, which still isn't totally standardize. For Mercedes after 2016 the 11th character is used to indicate production location. Keep in mind the more on that first link :
This chart is not applicable to Mercedes-Benz products produced outside USA or made for markets other than North America. European/World market cars use a different system for encoding VIN numbers.
That said, according to Mercedes themselves, there are certain models actually made in the USA:
- GLE (Coupe & SUV)
So what I can extrapolate from this, is that Mercedes-Benz is the brand, not necessarily the company, and the "WDC" is used to show what corporate entity produced the vehicle. I think this is why they have Daimler-Benz, Daimler-Chrysler and Daimler AG as 3 different codes. It's just part of their corporate evolution.
I haven't been able to find the Euro version chart (at least not a current one), but you may have better luck. I think, with me being in the US, Google is "helping" show "applicable" results and not the correct Euro information.