Let's be clear about something, the threats from exposing our information are not hypothetical, the last 10 years of repeated hacks into banks and services that

Let's be clear about something, the threats from exposing our information are not hypothetical, the last 10 years of repeated hacks into banks and services that expose people's financial and personal information (CC numbers, SSN numbers, etc) is proof that there are adversarial actors actively trying to get and exploit our information for financial gain. Right now, a database with structured data is useful (and amazing that its not encrypted in a way where it would be useless to steal at rest), but if you were able to get a treasure trove of unstructured messages we may not be far off from being able to extract a ton of information from that too. And that's just financial stuff. The current generation has repeatedly proven that they want to send revealing photos on these chat platforms. Remember the iCloud leaks of revealing photos? These were done with phishing attacks, but once again proves that there are malicious actors looking to take what most of us would consider to be private personal property. Today it was phishing attacks, but without encryption, tomorrow it might be an actual massive data dump of every photo ever sent on Messenger. Again, we currently have AI models that can do facial recognition and that can do nudity detection (as employed on YouTube, etc.), so access to the data set of photos sent on Messenger could then be analyzed by a computer to extract all nudes of key people (if targeted), or just all nudes (if not targeted). If your response to this is "they shouldn't be using it that way" -- again, consider that you might have second-order exposure to this problem. You may be smart enough to not send compromising information on Messenger, but maybe a close family member isn't and now you can be blackmailed or extorted to prevent revealing something of theirs. Or let's say everyone in your family is smart enough not to use Messenger this way. Your representative or senator's relatives might not though, and now they can be blackmailed too, and there's not much you can do about that since you may not even find out. All these problems similarly exist with respect to corporate privacy as well (trade secrets vs. potentially malicious foreign companies, people trying to get inside information for trading, etc.) At the end of the day, to me the question of whether the US is trustworthy is besides the point: the lack of encryption exists for anyone trying to get in, and we know there are bad people trying to get in. If you take the lock off the door you might trust your friendly neighborhood policeman but the cat burglar can just as easily turn your doorknob.