They can’t defend those “gains” you mentioned. They could be retaken within 24 hours.
China’s overextended. Trump’s economic pressure is an existential threat. China will deal.
However, given all their container ships; all the soldiers they could put on them . . . I think it might be tempting to underestimate China.
Then there is their DEEP rooted Chinese pride and resolve to MAKE CERTAIN this is the CHINESE CENTURY, if not Millennia. They really believe it IS 'their turn' to rule the world and that America is falling like Rome.