International users that have Advanced Protection enabled would in theory be safe from all of the 3-letter agencies (like safe from those agencies getting the data from Apple...not safe generally).
Realistically we are talking about FISA here, so in theory if the FBI gets a FISA court order to gather "All of the Apple account data" for a non-us person, Apple would either hand over the encrypted data OR just omit that....
Based on the stance Apple is taking here, its reasonable to assume they would do the same in the US (disable the feature if USG asked for a backdoor or attempted to compel them to decrypt)
It's worth pointing out that just because the FBI didn't have the access they wanted, it doesn't mean that other agencies don't, or that the FBI couldn't get the data they wanted by other means (which was exactly what they ended up doing in that specific case). It just means that they wanted Apple to make it easier for them to get the data.
It's good that Apple refused them, but I wouldn't count that as evidence that the data is secure from the US government.
It's also worth noting that the US courts have long held that computer code is speech.
Apple's legal argument that the government's demand that they insert a backdoor into iOS was tantamount to compelled speech (in violation of the first amendment) was going over a little too well in court.
The Feds will often find an excuse to drop cases that would set a precedent they want to avoid.
Would your answer be the same if this encrypted data was stored in China instead of US?
I don't think messages should ever leave the device, if you want to migrate to a different device this could be covered by that user flow directly. Maybe you want to sync media like photos or videos shared on a group chat and I'm fine with that compromise but I see more risks than benefits on backing up messages on the cloud, no matter if it's encrypted or not.
I think the average human will disagree with you. They want to preserve their data and aren't technically competent and organized enough to maintain their own backups with locally hosted hardware. Even the technically literate encourage _offsite_ backups of your data.
Know your threat model and what actions your trying to defend against.
Typical humans need trusted vendors that put in actual effort to make themselves blind to your personal data.
Realistically we are talking about FISA here, so in theory if the FBI gets a FISA court order to gather "All of the Apple account data" for a non-us person, Apple would either hand over the encrypted data OR just omit that....
Based on the stance Apple is taking here, its reasonable to assume they would do the same in the US (disable the feature if USG asked for a backdoor or attempted to compel them to decrypt)