Not sure why you guys think Chinese infantry superiority would somehow trump US technological superiority. China just recently got their first Air Craft carrier and they bought it. US Naval force projection coupled with air superiority would prevent a massive invasion across the pacific which would be damn hard to cloak for the amount of troops China would need in order to have a successful invasion of the US. Not to mention in this scenario a Chinese invasion of the US would trigger NATO provisions for mutual self defense, as well as the US-Korean defense treaty. China would not just be fighting the US if they were to invade they would be fighting South Korea, the Philippines, and all of NATO....It should be noted the US and NATO members are China's biggest trading partners, the economic effect of an embargo from these two members would absolutely cripple the Chinese economy.

We are also forgetting China doesn't even have the navy necessary to even begin to undertake such an operation as an invasion of the United States, and the test bed for any Chinese attack against US interest is Taiwan, of which China will not invade due to US Naval Superiority in the region which would make an invasion near impossible to supply, and that is WAY closer then the US West Coast.

Numerical superiority in ground infantry can only get you so far. Without combined arms fire (major US military doctrine) it becomes damn near useless. It's great to have 1 million men fighting 300,000 as long as those 300,000 aren't calling in naval bombardment, coordinating with armored cavalry, air strikes, and artillery bombardment. It's a force multiplier effect and China currently has no answer to US Naval supremacy in the region especially not US Air Craft Carriers.

Besides both the US and China are nuclear powers, and even if it came to that the US could possibly limp on after a Chinese nuclear strike considering the disparity in nuclear arms is massively stacked in the US's favor, 1.2k warheads compared to ~250.