True, the number of accelerators there is scanty
Nvidia is prohibited from supplying most of its modern AI accelerators to China, and even more so the flagship H100. However, such adapters are reported to still end up in China.
Chinese artificial intelligence researchers have the Nvidia H100 at their disposal. In particular, they were repeatedly used in their work by scientists from the National Science Institute of China.
What's interesting is that this is not some kind of secret information. Data on the use of H100 is available directly in scientific articles that are published in the public domain.
However, it is impossible to say that US sanctions do not work. At least in known cases, Chinese scientists used only systems with a small number of accelerators: up to a maximum of eight cards. Compared to the thousands and tens of thousands of adapters that Western IT giants purchase, this is just a drop in the bucket.