I think you mean "overtly mandatory" in China's case.
The overt, pervasive mandatoriness of the Chinese system is another ballgame entirely.
If the Chinese gov't shows up and asks for basically anything, of course you give it. There is no questions, no lawyers. It is how things are done.
US tech companies do have lawyers and fight back at some stuff. Think about all those defamation cases where people try to sue Twitter to get the identities of people criticizing them.
How do you think that works in the Chinese social environment?
Technical issues are a bit different though. Australian intelligence does not have rooms in any AT&T building I think. Though perhaps they perform some legal tricks to give them access and then roundtrip the info.
I hope they at least feel bad doing so.
It is entirely possible that without being told neither government could have become aware of this in spite of having the communications that could make them aware if only someone read them. It's also entirely possible that the Chinese government became aware from being told by folks at those Chinese companies who received disclosures, and that the U.S. government wasn't. Eventually we might find out what the actual situation was.
From a purely legal and policy standpoint, the linked report is concerning. One would think that Intel ought to be aware of the national security implications of Meltdown/Spectre and should have alerted someone in the U.S. government, though they're probably not obligated to. And, of course, what if Intel had not be an American company?
Doesn't that mean that it is a “near certainty” that the U.S. Government was aware of it, because authorities (NSA, etc) routinely monitor all such communications?