For open source messengers, you can check whether they actually encrypt your messages and whether the server has access to your encryption keys but what about WhatsApp? Since it’s not open source, you can’t be sure that the encryption keys aren’t sent to the server, right? Has there been a case where a government was able to access WhatsApp chats without reading them from the phone itself?
If you did not enable end-to-end encryption for your WhatsApp backups on Google Drive, the US government could possibly compel Google to hand over your encrypted (but not end-to-end encrypted) backup, and compel Meta to hand over the decryption keys for the backup.
Details about how WhatsApp backup works: The Workings of WhatsApp’s Backups (and Why You Should Enable End-to-End Encrypted Backups).
