There are a lot of political issues for a US company to do business in China. Add to that a US patent is worth about as much as the paper it was printed on in China.
It’s not uncommon for US companies to work with Chinese companies. In most of the partnerships the design is sold by company X (US) to company Y (Chinese) with an agreement that it will only be sold in certain markets (usually markets that company X can’t easily get into). So now when a competitor steals a design, you have a local (Chinese) company and a US company they must deal with.