The Russian election meddling is more exaggeration than fact. At the end of day, the American government can order Facebook or Twitter to delete content and accounts at any time.
Even if Russia was behind the Fake News activity, they were tolerated because it served the purpose of one of the American factions. In contrast, China has no sympathetic faction in the US.
China's GFW is highly effectively at blocking foreign subversion, but it is also a double edged sword as it creates a segregated content sphere from the rest of the world.
What China needs to do now is to push its content platforms toward a global audience. We are already seeing the tip of this push with the growing popularity of Tiktok.
China doesn't need sympathetic factions in the US. In fact, the so-called faction that is sympathetic to Russia has done little good for Russia, Russia's situation after the Trump administration took office has NOT improved at all. Those Americans only use the name "Russia" as a mean to push for pro-white rhetoric. They didn't help Russia at all. East European NATO countries actually became more confrontational against Russia. Poland is ordering F-35, and Ukraine is drifting more and more towards the West. The strategic Russo-German relations are under more and more scrutiny from the US.
These social media "unconventional warfare" are not meant to cement good relations between societies/countries. They are ONLY meant to create internal division within the a society. The Russian understood this. They were NEVER expecting a more pro-Russia US administration, that wasn't what they strove for. They strove for a more divided US. As long as the US is more divided, the Russians don't care that the incoming administration ending up being more hostile towards Russia.
Just like how the CIA who roused up the HKers, they weren't doing this to make HK-US relations better. They were never doing this to cement good relations with the US. They were doing this to wreak havoc in HK society. They don't even care if it back fires and HK people ends up hating US more. As long as HK society become more divided, the US's goal is achieved.