I do see your point about the local plants. I've got grief about where some American manufacturers do the manufacturing also.
From what I understand, most of the hard parts are made in Japan for those cars, and they are assembled here. For American cars, I believe that most hard parts are made and assembled here. I'm not going to say all of them because I know that's not true. The point is that these are the plants that employ people. The Mercedes plant is great, but I think that we're talking about cars under $50k or $60k.
And, as far as replacement parts, no one is more expensive among these than Honda and Nissan in my view. Toyota isn't cheap either. Not only that, you can buy an American made aftermarket part for an American car and it will probably work fine.