“China has much more potential than the United States on account of its much larger population.”
I’ve never, ever understood this line of reasoning. It has never made sense historically. Its huge population could work against it just as easily over the longer term. If mere population size was the dictator of potential, history would look quite vastly different.
All of the mentioned civilizations in the earlier bulleted post had (comparatively) huge populations, if not the largest population in their region. Both the Roman Empire and Ancient China were estimated to have a quarter of the global population, each. Western Europe "picked up steam" (appropriate for this sentence) after the Industrial Revolution allowed for an immense increase in population (more medicinal practices, more food, etc.). There is a large correlation between population and power.