There are those in the NA auto industry that complain that the Japanese Federal Govt. helps keep the yen/dollar exchange down (ie. the yen low) in order to allow Japanese companies to better compete in the NA market. Is there truth to that? Maybe, but like a lot of things in the area of global economics, it is not quite that simple.
The Japanese companies are quite sensitive to criticism, which is partly why nearly all of them have built substantial manufacturing plants in the US and Canada. They do not wish to "rock the boat" as to Japanese companies having an unfair advantage. There are some in the US unions that still believe that Japan is an enemy.
Actaully, it is unlikely that Toyota, Honda or Nissan would like to see any of the US Big 3 fail. It would put more heat on them - and the US ppl can be quite "protectionist" when their own ox is being gored.