Japanese car company stocks exploded while GM's dropped. Fairly easy to see who "won" the deal. US car makers aren't going to sell a single car more in Japan while their cars now have an advantage over others, and Japan can really use rice imports at the moment, rice prices are becoming a huge problem for the government. Not that the US is exporting or even producing a whole lot of rice anyway.
Trump's really a master of negotiation and deal making. His tarrifs are now screwing over GM more than Mazda, Toyota & comapny.