George Friedman and Peter Zeihan say that it is not clear that China would win a war even just against Japan.
Both countries rely on imported oil. The most likely cause of a war between them is an oil shortage, giving nations an incentive to use their navies to capture oil tankers. The use of navies to capture cargoes of national importance was common for centuries till end of WWII. It ceased after WWII because of US naval dominance combined with the use of free trade as a part of US strategy in the cold war, but of course the cold war is over; so the US, which has been and remains the power least reliant on international trade, could choose not to spill the blood of US sailors to keep the sea lanes open to all.
Japan knows this and has been building a navy that can operate outside the South China sea and in the Indian ocean, so that it can escort oil tankers from the Persian Gulf to Japan. China's navy in contrast cannot operate outside the South China sea, he says.
Friedman says that aircraft carriers benefit a country only if it has admirals that know how to use them and points out that Japan's admirals have been trained by admirals trained by admirals that actually used aircraft carriers in a major war.
The main purpose of the People's Liberation Army is to put down a rebellion by Chinese citizens. The primary goal and concern of the rulers of China beyond their Party's remaining in power is to prevent the country from splitting apart. For most of the 2500-year history of China, it has been divided into multiple polities, and outside powers have played the pieces off against each other.
The US just lost a war against the Taliban, a war it spent many trillions of dollars on, so I doubt the US military worries about whether a loss in a future conflict would signal an end of US hegemony.