It depends on how you define war.
The US military could easily win the battle against the Chinese military if they went toe to toe, even with allies the USA would probably win.
That doesn't mean the US could hold the chinese mainland for very long. Over a billion people would simply be nearly impossible to manage. Especially if they were hostile to you. If the USA and allies were in an iraq like situation in the Chinese mainland it would be bloody expensive. Of course war isn't always about occupation either.







