But, since the Nobel was established, China has been invaded by Germany, Japan, Russia, Britain (largely India), France, the United States, Italy, Austria-Hungary, and Japan again, and had a civil war which hasn't technically ended (plus the end of the Boxer Rebellion), a revolution, and the worst famine in human history. But probably the worst event for its Nobel chances was https://en.wikipedia.org/wiki/Cultural_Revolution. The civil wars also brought to power brutal dictatorships, including in the so-called Republic of China.
The US has been invaded zero times and had zero civil wars during that period, and in the US, the Cultural Revolution and dictatorship are just starting. Consequently many people who might have been Chinese, German, Japanese, Russian, etc., during the period in question were instead born in the US. And note that, on the page I linked above, 6 Nobel laureates from the US were actually born in China: Charles K. Kao, Daniel C. Tsui, Edmond H. Fischer, Yang, Tsung-Dao Lee, and Walter H. Brattain (!).