US GDP per capita is still almost 8x that of ChinaOne reason this might not be the right metric is because absolute power of a country matters more than power per citizen. Imagine a country with only one citizen, but a trillion dollars. The country wouldn't be very relevant. Even if the citizen tried to hire a military and use it, they wouldn't get very far. They wouldn't exert much influence economically either, in the sense of causing other countries to become dependent.
Also, total number of citizens is an important metric in itself. People in both the US and China will pretty much do whatever their power structures tell them to do. If that means beating a war drum, there are going to be a lot of people agreeing with war on both sides, but far more in China. Overwhelming forces can be stopped with tactics and technology, but when technology is comparable the casualties are usually comparable. And China has been gathering our technology for a long time.
War isn't the concern right now, though. The example was just meant to illustrate that China seems to have more options than the US.
As China grows richer, I expect the US will too. In modern inter-connected economies with few trade barriers growth in one generally benefits the other too.
History seems to disagree. As one country grows richer, other countries tend to become subservient. There's no such thing as modern human nature.