I hope you are joking about the Mongols....
The city of Baotao in Inner Mongolia can beat Mongolia. On its own. The entire Inner Mongolian Autonomous Region would just be total overkill against Mongolia.
Anyway, it's not quite true - China had faced sea-borne threats before the 19th century - the wokou is a notable example unless you mean 500+ years by recently.
To be honest, 200-1000 is a long time off so as to make geopolitical speculation almost pointless. 200 years ago Napoleon was about to march on Russia and the gravest threat faced by the United States was internal cohesion, in China, foreign merchants were corralled in factories, and the Maratha were still contesting Company rule in India.