Suppose China becomes a significant part of Google's business in a number of years. Does anyone familiar with China doubt that its government would be willing to exercise that leverage over Google to extract private user information ... even about it's non-Chinese userbase?
How would future Google respond? Would there not be a gigantic financial incentive for Google to hand it over? Would it be willing to leave the Chinese market to withhold its user's personal data?
None of this is certain, but the risk is real enough imo that it makes me uncomfortable as a US-based Google user.
Sure, you can argue "well the US has done this in the past" but A) it's much more possible for Google to say "no" in the US, and B) the US government's interest in such data has historically been limited to (admittedly arguably overzealous) national security concerns, whereas the CCP's interest in such data seems to be for "whatever we can get out of it."