There is no auto-wipe feature like that. You can use auto-reboot feature that will put the phone into BFU state even in a Faraday bag... It will make it harder for them to unlock the phone unless you give your PIN.
There is SeedVault backup but it doesn't backup all the data, the best way is to manually export/backup any important data you care about.
On a general note, if you have a grounded concern like this it would be better to preemptively wipe your phone before crossing the border and store any needed data in the cloud... Do not carry sensitive data on a physical device with you even encrypted... You unwillingness to decrypt may cause far worse problems... in theory at least...