Some years ago, before the financial crisis, I used to beguile the time during my 3-mile runs by keeping score of how many Asian, European, and American cars passed me (Asian, because it taxed my memory too much to try to split out the Korean cars, which at the point were few). Typically, slightly less than half the cars I counted would be Asian (though not uncommonly a bit more than half), with Euros and Americans more or less splitting the difference. A representative Asian-European-American split would be something like 34-20-17.
I stopped doing this for a long time, partly because I switched my route to more off-road, mainly I think because I just got bored with it. Recently, I started up again -- not sure why. And I'm here to report that if the convalescent U.S. auto-makers are doing credibly in the U.S., it's in parts other than South Orange/Maplewood, NJ. Here, according to my unscientific survey, the number of domestic cars on the road has collapsed -- and Asian cars have gained on Europeans, too. My most recent count was 52-19-7 (wrote that one down); another was something like 37-14-5. (Of course, given my hiatus, this difference tracks what's happened over the last few years rather than the last few months.)
Though I have no evidence, the cars passing me on balance strike me as older on average than they used to be. If that's true, I wonder if it's helped tipped the balance. Japanese cars last longer than American ones, maybe longer than European ones, too. Therefore, the proportion of Japanese all cars on the road may be higher than the Japanese share of new cars; the older the average car, the higher the proportion of Japanese. (Though I must say, I think new GM or Chrysler cars are rarer than the dodo bird in my parts. I do see a few new Fords.) Meanwhile, the Koreans have grabbed a bit more market share on the new car end, which at least marginally runs up the Asian score.
I'm blowing some speculative smoke here, no denying. But I'm quite sure that there are fewer domestic family vehicles on the road in my two towns* than there were three years ago. Maybe partly because there are fewer SUVs? I have no evidence of that, either.
* Today, driving on I-77 in North Carolina, I tried to keep a similar score, but soon gave up because I kept passing and getting passed by the same cars and the meridian was too wide to identify the oncomings. Nonetheless, I can report that in maybe a half-hour of keeping track I didn't see any European cars. There seemed to be a roughly even split between domestic and Asian. What's up with that? There were plenty of mcmansions in the area; do Audi, BMW etc. have no toehold down here? Or was the tiny sample nonrepresentative?
UPDATE 9/4: Re new American cars: they exist! Just took a run in Buffalo, out by the marina, and the Asian-Euro-American count of moving cars (I ignore parked cars, because at home they're always the same) was 13-6-26. I saw quite a few newish Ford Focuses and Fusions as well as newish Chevvies - Cobalts and HHRs, I think, looking after the fact at the Chevy website, and maybe an Impala or two (as well as a good share of American SUVs).