I don’t think they care, which is different from actively wanting Americans to overdose on the streets. It provides them with a ton of propaganda (internally and abroad), and it demoralizes the enemy. They’ve offered to cooperate to combat the drugs, but the US either refuses or demands that China jump through a bunch of hoops while the US does nothing (like how they demand Mexico combat cartels, reduce poverty and migration, while also taking in other migrants and producing food for the US, while the US just needs to shoot people at the border), or they simply demonize the Chinese instead of working together. Even the DEA has praised China

"It was all coming through the mail, aircraft, not in large quantities because it was so pure the fentanyl that they were making over in China ... but once they classified entire analogs of fentanyl, it made a huge difference," said Matt Donahue, the DEA deputy chief of operations who oversees the agency's work abroad.

While stricter regulation has not wiped out the fentanyl-related industry in China, it has made it more difficult for illicit vendors to operate.

If your neighbor is crazy, it’s best to just leave him alone than try to fix the problem on your own or mend relations with him.

https://www.npr.org/2020/11/17/916890880/we-are-shipping-to-the-u-s-china-s-fentanyl-sellers-find-new-routes-to-drug-user

Pretty much all western media report that it’s companies that are skirting chinese laws and inspections rather than the laws and inspections being lax - and of course local corruption. The only people who believe that the government and party are actively trafficking drugs as part of their agenda are cranks