Comparing "the US" and "China" is comparing apples and oranges. China, like the rest of East Asia and most of Europe, is an ethnic-based country, whereas the US, like Australia, Brazil, and even the UK and France, is an immigration-based country. Generally, Americans don't become Chinese, nor would they want to. That's the key for why the US will remain tog dog. Of course, there's other factors: the US military control of the world's oceans, and the under-utilization of the Mississippi compared to the Yangtze or Ganges. Talking about China's skewed population distribution or lack of innovative freedom are effects, not causes, of the ethnic- or immigration-based nature of the two countries.
China is actually quite diverse, both linguistically and ethnically speaking. Also, as regards immigration, China is beginning to able to attract foreigners to their research institutions. Money wins. The U.S. would be wise to re-learn this lesson.