I don't know what the exact procedure is for deportations when it comes to the US, but shouldn't those who are deported be allowed to take at least some personal belongings with them?

If that is not the case, then the only way for a deported person to regain possession of their backup is to encrypt it and store it online, and try to remember the password. In that case, you would have access to your backup anywhere in the world where you have internet access.