China's land area is approximately 25 times of Japan, def has a bigger network. But the top speed is comparable in current generations[1] except the Maglev.
I would think that the vast amount of central/Western land in China that is sparsely populated might skew this statistic quite a bit, where Spain and Japan don't have that at the same scale.
1. https://www.railway-technology.com/features/the-10-fastest-h...