I believe that M-Class drive trains come from Germany. There has been so much trouble with the parts of the ML sourced in the U.S. that I've never given it serious consideration.
I'm more interested in the X-5 because it appears to be one BMW that's better quality than the Mercedes competition but now I hear that they aren't perfect either.
I've been buying German cars since the 50's and Mercedes for the last 19 years. However, it appears there is really good evidence that Toyato and Honda are a lot more bullet proof than the Germans.
If I have to replace the head gasket in my low mileage '91 300E I'll probably go Japanese next time.