A counterpoint here: Consider American subpoenas, court order, FISA warrants and the like. Remember that FISA warrants are secret! Having the data managed by a US company has these consequences. Perhaps you trust the US government more than you trust the Chinese government... that is very reasonable, to be sure. But it makes so much more sense that your data is subject to the law in the country you reside in, rather than the laws of a foreign power.
This is not even remotely hypothetical. Making everyone's data accessible to organizations and people subject to US court orders is bad for privacy.
This kind of thing will be happening more and more, and not just China and Russia, but also the EU. So it won't just be that Chinese users can be spied upon by the Chinese government. It will also be true that it will be more difficult for the US to spy on citizens of other countries.