Exactly, imagine a US company supporting Tibet/Dalai Lama or Falun Gong etc. China would most definitely ban them from doing business in China.

Do you have an example for that? I looked around a bit and only found China not buying from weapon manufacturers anymore who also supplied Taiwan. When it comes to pressure on topics like Tibet they seem to mostly pressure countries instead of companies.

Is China trying to enforce any kind of similar ban? I got the impression that trying to enforce unilaterally imposed global sanctions is a US thing. The next best thing coming to mind are UN embargos