Math results of the best performing US state, Massachusetts, was actually 20th and 9th in the world for PISA 2015 and 2012, respectively, according to the links below.

Moreover, MA's population of ~7 million is only ~2% of US population, whereas the four provinces' 180 million is about 13% of China's population.

"for the Program for International Student Assessment, or PISA. It shows the state is tops in the country in math, but when you zoom out and look globally, Massachusetts ranks 20th in the world."

https://www.wbur.org/edify/2017/04/10/massachusetts-math-edu...

"I found that if Massachusetts were allowed to report subject scores independently ... the Bay State would rank 9th in the world in Math."

https://www.forbes.com/sites/jamesmarshallcrotty/2014/09/29/...

I think there should be a clear-eyed view toward China's progress in education as well as advanced research. For example, based on some measures of publications in top AI conferences, among the top 10 academic institutions in the world, 4 are in China, 4 in the US, and 2 in Singapore.

http://csrankings.org/#/fromyear/2018/toyear/2019/index?ai&v...