Why is there such a big gap between China's computer skills and the United States?

Different national conditions. In China, people who can use computers to do special effects are basically not in the game industry, nor in well-known foreign companies, and there are many such special effects artists from the Academy of Fine Arts.

Domestic special effects artists are basically second-rate, and most of them become monks halfway. Many of them are computer programmers who switch to special effects artists, so there is probably nothing they can do about film special effects that require artistic sense. This is essentially different from foreign special effects artists.