There's a belief that the Chinese want to fuck the West in revenge for the Opium war; there's even Chinese supremacists that support this idea. However, the Chinese have taken measures to stop fentanyl production, so that might not be so true.

Ketamine is a tricky one due to its legitimate production and uses, especially as a local anesthetic in the third world and for veterinary stuff. But a lot gets out to the wrong people and used for inappropriate purposes. China is actually pushing other countries to make changes to international laws to control Ketamine more strictly, because of the negative effect it has upon Chinese society, but many in third world oppose such proposals.

As for Meth, that's relatively easy to produce domestically anywhere. It was mainly kept out of the UK for years by coke dealers who disliked it as it was far less profitable; but the Eastern Europeans brought it in. I'm not sure if we can always blame the Chinese for all meth issues outside of China.