Privatizing USPS would take a Constitutional Amendment. If you don't remember what that hurdle is, review the US Constitution. You'll also see that the post office is a federal goventment institution. You might even have lived near a Post Road, e.g. US 1. Did you ever wonder how it got that name?
As to Amazon deliveries, if you are a Prime customer you can opt for Key (in-garage) deliveries. That is nice for several reasons. Mis-delivery is impossible. The package is not exposed to theft. It is not exposed to the weather, except from the truck to your garage door. You also will get a notice upon delivery. You could even install a camera in the garage if you are concerned about what happens while the door is open.
Yes, most garage doors in TV are made by Linear and the Chamberlain based MyQ won't work with them. They also probably are not wifi enabled. But there is an alternative. Check on Amazon to learn about
Amazon Key. It is fairly simple to add wifi support to your garage door opener. You can even allow trusted friends or relatives (with smart phones) access, if you want to, without needing a standard remote control.