Today, there is 413GW of nuclear capacity globally. Of that, 57GW is in China.
China plans to reach 300GW of nuclear capacity by 2035. Assuming linear growth, that number will be around 550GW by 2050 (more than double the current global nuclear capacity) There are currently 57 nuclear power plants under construction. 21 are in China. 1 is in the US.
This US pledge is basically useless.
In the US. In China, nuclear reactors go from first pour to operation in 5-6 years. Economies of scale apply.