Why does this argument "lose merit" when it addresses transplants only? If you discount the Aveo and GTO and Saabs...and most of the Lexus and Scion brands (and a handful of Toyotas), that seems to be the appropriate comparison. Toyota produces well over a million vehicles a year in North America and, by your numbers, they have over 70% domestic content.Domestics are making more "imported" vehicles and the foreign-based companies are expanding their US and Canadian production. Toyota and Honda and Nissan are hiring more workers in the US and Canada while GM and Ford are hiring more workers in Mexico, China, South America, and Europe to replace closed factories and suppliers in the US and Canada. Why is this a pointless fact?
Secondly, have you ever read the law that defines "domestic content?" It gives domestic manufacturers an edge in the calculation. I don't recall the specifics (you can read it for yourself), but the same part can be "imported" or "US/Canadian" depending on WHO is putting it into their vehicle. The example I recall explained how two vehicles built in the same North American plant would count the exact same part (from the same source) as "imported" or "domestic" depending on who's vehicle it was put in. The law favored the domestics.
Third, while new transplant jobs are not replacing lost Big3 jobs 1-for-1, this is not the fault of the transplants. For years, the Big3 have been forced to have a bloated workforce. They have far too many workers for the number of vehicles they produce, and it's not their fault. The transplants have established new factories and supplier bases who do not come with the legacy (read: UAW/CAW) costs and can staff up or down to their requirement. Nissan, for example, has had among the fewest workers on the line per vehicle built for many years while GM is required to keep a certain employment level, whether or not those people are actually adding to the productivity of the plant.