Canada

While better than nothing, you want to avoid using the OS's cloud for backups at all, as that means your data is unencrypted and accessible on Googles/Apples servers (for 99% of smartphone users). There's nothing to stop the American nazi party from using the NSA's privileged access to scan every account for wrong-think.

Ideally you want to perform a fresh encrypted backup on a PC and upload that to multiple cloud services — preferably EU and E2E encrypted — then download and restore it once you pass through customs at your destination.

TIPS:

• This is not just for the US. Almost every customs can image your devices at any time.

• it's best to setup a "travel image" for every device, that is adequate for the entire trip, in case restoring from backup fails.

• just deleting everything is not sufficient. Logs, caches, etc all persist on a device; many of which are completely hidden from the user.

• do everything a few days or more beforehand so you have time to trim the fat, upload the backup, and setup the new travel image with the core apps you need for transit.

• It's best to remove all photos and other large non-essential app data before performing this backup to keep it as small as possible.

• do a screen-recording as you click through all your OS and app settings, pre-backup, so you can setup the clean "travel image" how you like it.

• setup a separate password manager account, and only use it to store credentials for critical accounts while transiting.

• keep 2 separate 2FA and password manager backups in a reputable E2E encrypted cloud provider, accessible by a memorized passphrase you use nowhere else. I do this in general every so often as part of a standard backup routine.

Yes, it is ridiculous for law abiding citizens to have to do any of this to protect their privacy and data sovereignty, but this is the reality of living in corporate oligarchies hostile to civil liberties and human rights.