I think that these protectionist measures are ultimately going to hurt the competitiveness of the US auto industry. Exports and international sales are a big, but not overwhelming part of the revenue for major manufacturers. It's something like 20% of GM's revenue, and maybe 35% of Ford's. When they can't compete internationally, it's small enough that executives will convince themselves to focus on their core market…
In a way, its funny you say Toyota is the foreign brand. Of domestically produced GM, Chrysler, or Ford vehicles, most are shipped to foreign customers; of domestically sold GM, Chrysler, or Ford vehicles, most are manufactured by foreign factories. They do some assembly locally, but the majority of it is of foreign manufacture. However, Toyota manufacturers most of their domestic sales domestically, and operate one…
I still think it's a useful distinction though. There's also a whole lot of people involved that aren't on the production line (like me). The corporate culture is also very different between the American and Japanese conglomerates I've worked for.