I agree that Chinese control of users' private information is alarming.
But what makes anyone think that selling such software to someone in the US makes it any safer than if China owns it?
Big US social media businesses (Zuckerberg, Musk) are famous for harvesting users' private information and selling it.
The US government (following Snowden) is famous for taking, storing and using the data of non-US citizens for its own unknown purposes.
And then there's the possibility of another Trump presidency and the data's potential use in the future for the purposes of extortion etc.
If Mnuchin's purposes were benign and protective, he'd secure the data in Switzerland. That isn't what he is planning. He wants the data for commercial and probably governmental reasons.
Sorry to say it, but the US is not the white knight in this tale.