To be fair, boomgear is not some national conglomerate, they are just a performance shop with an owner passionate about racing. When I visited the store, his whole shop was just filled with racing trophies and various cars being worked on.
How many US small businesses compete on the international stage? Very few and they probably have their reasons just like boomgear. Also ecu unlocking has always been a guarded secret, they don’t want to share too widespread because someone else could steal it.
Also, Chinese companies have tried to compete international but banned either for national security reasons or some other reason. Just look at their EV industry, basically banned in North America due to tariffs and Huawei (their equivalent of Apple/Cisco) being banned on ground of national security and the US government asking all their allies to do the same. When 2 diametrically opposed superpowers are competing, they each give unfair advantages to their own companies.
I think the Chinese would love to have large motors, but the truth is their older cities have roads as tiny as Europe and their emissions regulations seem to be as strict or stricter than Europe. Every countries car culture is different because of government influence/infrastructure/marketing