There is a concern dating back many years that a government will mandate that UAs trust a particular government-controlled CA (that eventually, but maybe not at first, openly performs MITMs). This is one reason that browsers really want to keep control of their root programs and not be mandated by governments to include any particular trusted roots -- including to maintain a remedy against roots that do appear to deliberately facilitate MITMs.

Although there have been lots of concerns about CNNIC, I don't believe that the Chinese government currently either (1) routinely uses CNNIC to perform MITMs for censorship or mass surveillance purposes, or (2) purports to require UAs to trust CNNIC or another Chinese root in order to be used by Chinese users. I'm happy to be corrected if someone knows otherwise.

They wouldn't "routinely" abuse their root to monitor large populations. That would be too obvious and result in near-immediate loss of their precious root.

What's more dangerous, and much more likely, is that they might use forged certificates against specific individuals for a short period of time, for example, to intercept login credentials. The attack will go unnoticed as long as they also block the corresponding HPKP reporting URL (if the targeted site uses HPKP at all).

I think this distinction is a good one, and I'll try to be more attentive to it when writing about this in the future.

Hopefully the risk for the attacker from the two kinds of attack are gradually converging, due to pinning and especially Certificate Transparency.

revoking the root outside china will have no bearing within. All devices sold and used in china could be forced to include that root. There is not a lot a user could do , especially in mobile if you have locked phone and only access to the official app store

There's a fine line between cartoon-villain evil, exemplified by people like Kim Jong Un who just doesn't seem to give a fuck, and just-enough-to-achieve-your-objectives-but-not-enough-to-make-too-many-people-notice evil, which is what China is aiming at.

Lots of people travel in and out of China with all sorts of computing devices. China does care about the reputation of their root and of their highly profitable electronic exports.