Maybe the question could be…who builds the most reliable cars, union or non union labor ? IMO, the answer to this and the one asked has nothing to do with where it’s built or who builds them. It’s one of the few times trickle down determines reliability. Buick had a string of exceptionally reliable products, even when their brethren used similar components. They encorporated real time subcontracting parts manufacturing along with instant communication between service centers and manufacturing lines which provided immediate corrections to prevent problems from being persistent.
These and other strategys have less to do with location and more to do with philosophy. Honda built solid products in Japan, the US and probably subcontracts reliable parts from China…same as Apple, same as John Deere etc.