Most of the people who sell and service union made cars are not in unions either. Also there are many shops that make parts for these cars that are non-union. So, people can support overseas makers if they want, but it does affect all Americans in some way.
I work on a lot of cars, trucks, tractors, motorcycles, etc., and I'm not union!
Also, outside of warranty work, NONE of my vehicles have EVER been to a dealer for service.
Unfortunately for dealers, my sons and stepsons have followed in daddy's footsteps, and one works at a NAPA store. All 5 of them do their own oil changes and tuneups, all but one has changed an engine/transmission, or helped me do the same.