Japan would ditch treasuries and US dollars. That would make the borrowing cost to go up. what if China follows the same playbook?
Honda is building a plant in the US. Japan buys $60 billion less from the US than the US buys from Japan. Trump wants fair trade which will cause the demand for dollars to increase.
a) Since there are no countries in the world with a GDP as large as the USA, it is unlikely than any country has the resources to buy more from the USA than the USA buys from them. b) In Japan they drive on the left, but most USA car manufacturers will not make left-hand drive cars to sell to Japan. Japan on the other hand makes LHD cars for Japan, and RHD cars to sell to the USA and other countries. c) ALL the cars made in the USA are large cars. The small cars that GM and Ford sell are rebranded cars made in Asia. Due to the high cost of gasoline, most consumers outside the USA are not interested in buying large cars.
that's technical. we export/sell dollars, a lot, just print and buy goods from all over the wrold without lifting a finger. japanese car, korean cars and next will be chinese ev cars, as long as we can print and control the chokepoints militarily. now it hits a wall, every country wants to reset the financial order if not the world order, without a wolrd war.
Despite their very famous names, none of the brands you mentioned are even in the top 10 of worldwide sales. https://roadgenius.com/cars/statistics/sales-by-manufacturer/
maybe the op never look at non luxury car segment. i like germen cars very much and i did an european delivery for my first bimmer, a mb owner for the last few cars.