It's pretty hard to compare. If you just compare their budgets, then the US should win. In 2016, the US $521.7 billion on their military. China "only" spent $146 billion. The fact that the government isn't spending as much on the military doesn't necessarily mean they are that much weaker. "According to the Stockholm International Peace Research Institute, SIPRI, China became the world's third largest exporter of major arms in 2010-14" (https://en.wikipedia.org/wiki/Military_budget_of_China). This means that they are creating a mass amount of weapons for other countries. In the case of a war, the government could probably just seize many more weapons that are being produced there.