Any entity that knows so much about you can manipulate you in ways you won’t suspect. Their government isn’t held back by the Constitution and they probably wouldn’t hesitate to influence the citizenry of their main rival on the world stage.

The US government isn't really held back by the Constitution either. It's been diluted so much they can just use Canada as a proxy and return the favour, for example, no problem. I agree with your overall point but it's not really a legal matter, it's just power.

For non-US citizens the US constitution also has no relevance. Thus for non-US citizens it makes no real difference

I'm non-US citizen and still think that there is difference between US and Chinese government.

Tell that to Assange.

... the US government isn't particularly limited in such a way either. They have nice have for everything foreign communications, and all the actions are held as confidential

Sure, I also don’t care what the Chinese government knows about me. I care a lot about their ability to influence US elections though.

I'm much more worried about the ability of Google to influence US elections than China.