China has 150% more soldiers than America does, plus a high tech 'Kill Weapon' the U.S. can't deal with.
China has about 3.4 million active military personnel compared to America's 1.4 million. Moreover, in some key spaces, China might even have a tech advantage:
“After years of conjecture, details have begun to emerge of a "kill weapon" developed by the Chinese to target and destroy U.S. aircraft carriers.
"The size of the missile enables it to carry a warhead big enough to inflict significant damage on a large vessel, providing the Chinese the capability of destroying a U.S. supercarrier in one strike. Because the missile employs a complex guidance system, low radar signature and a maneuverability that makes its flight path unpredictable, the odds that it can evade tracking systems to reach its target are increased. It is estimated that the missile can travel at mach 10 and reach its maximum range of 2000km in less than 12 minutes."
"If operational as is believed, the system marks the first time a ballistic missile has been successfully developed to attack vessels at sea. Ships currently have no defense against a ballistic missile attack.”
Source: U.S. Naval Institute