The critical key here is economy and reinforcing time.
Economy translate to much bigger numbers that can saturate the enemy's defense and literally exhaust them of firepower and bullets (see Korean War and China's superiority in #s)
Reinforcing time is much better for China in an China-US war on Chinese soil, since China has a relatively industrialized production base with modern transportation capacity and can reinforce her troops quicker than America, whose main production facilities are over 8,000 miles away.
By the time adequate American reinforcements arrive, Americans would be pushed out into the sea or wiped out entirely and would be forced to sue for peace, or do an amphibious land assault like Incheon or Normandy. Even in that case, unless Chinese economy and industry completely suck, the Chinese can atleast hold America off on a stalemate with mass infantry alone, albeit with very heavy costs. Over the long term if Chinese economy and political will power can sustain such losses and replenish the losses at a reasonable rate, I think the high tech adversary will win in the longer run since reinforcing advantage diminishes.
This situation is on Chinese soil or immediate vincinity of China. This supposes China has a VERY strong economy, production infrastructure, and strong industry to equip, train, and supply mass infantry very quickly.
Summary: Pyhrric victory for mass infantry in short-medium term (at worse, an stalemate), and probable lost for mass infantry in long term against high tech adversary since if both economies of China-US are equal, reinforcing time advantage diminishes and high tech should be able to gain an upper hand by targeting production infrastructure of mass infantry nation.
But China isn't stupid. She isn't going to tdo mass infantry against US, she is going to mix in assymetric high tech warfare (anti-Sat, cyber, missiles, anti-access, financial warfare, etc..) to maximize her ability to deal damage against a high tech adversary.
China is pretty much going to destroy US in a war if the war occurs in China's immediate vicinity, esp. over Taiwna.