On American social media platforms, US, British, Canadian and Israeli astroturfs run amok. US has got numerous departments running propaganda and controlling speech. India also runs a ton. Case in point, here are 64 links showing that these countries (links are mostly evidence towards US propaganda) are running mass astroturfs online:

https://www.quora.com/How-are-you-sure-that-censorship-works-the-way-you-think

Also, look at bot upvote patterns and which false narrative are purposely being spread. Better yet, just look at how MSM in numerous NATO countries match the propaganda and fake news that's being spread on social media.

Logically, social media platforms would work with intelligence agencies of their own country.

China inserts a bit of money into propaganda outside of their own country. Their propaganda mostly spreads Chinese culture. Look at their Confucius schools inserted around the world. Every so often, you also get these mass upvoted Chinese cultural stuff on reddit's front page (see their migrating elephants, the way they pour tea, etc.), which is pretty much ineffective as a soft power tool since the NATO pedophiles have these "China is a shithole" mass upvoted threads on reddit's front page every week.

Russia seems to have minimal astroturfs running on US platforms..or at least they're not very apparent. And I haven't seen a single academic study with strong, concrete proof. The number of people going against mainstream narratives (especially during this Ukraine conflict) doesn't seem to be massive and it's mostly the same people who always look at both sides of the equation.