Also this argument is easily refuted by the US Postal Service, which physically delivers individual pieces of paper in a few days, for pennies.

Right but that’s a government service and it should be totally fine for them to deliver mail below cost using taxpayer money to make up the deficit.

Like every other government service - highways, defense, etc. They’re profitable to the system, but not per se.

USPS is fueled by parcel deliveries, but also in large part by literal tons of junk mail on dead trees; spammers have paid Uncle Sam handsomely to spam every citizen's mailbox for decades, and it's the most lucrative thing USPS can do with our home mailboxes.

The postal service is a quasi government entity that has operated (not to get too deep into the politics of it) for many years at a loss. It does compete with Amazon, as well as being used by Amazon, but it's very different as a business than Amazon.