The Big 3 used to refer to the three top US makes, but you make a good point. Sad, the US auto industry was unbeatable at one time. Now, it’s doing good just to get half of its home market.
Yeah, I realize it was a bit of a definition shift — however, the top three US makes used to be the world’s top three as well.
The notion of a “home market” is changing too. Some Toyota models (for instance) have more U.S. value-added than some models of nominally American brands.