It may be the case that a supplier who delivers something you didn’t request (in your case here) can’t make you pay, but they’d probably terminate any relationship with you.
So I’m only really going off of what the FTC says. In a case of an existing relationship if Amazon Subscribe and Save sends me an extra unit, then no I don’t have to pay for that. It doesn’t matter if I’ve been buying from them in the past.
"(1) Acceptance of goods occurs when the buyer (c) does any act inconsistent with the seller's ownership; but if such act is wrongful as against the seller it is an acceptance only if ratified by him."
UCC isn't law in every US state, but is common.
This may change somewhat if it is a business transaction, but I think it's quite clear if you get a package addressed to you that you didn't order, there's no contractual obligation.
As an example, if you have ever worked in retail sometimes you get truck shipments of things and there can be extra items you didn't order. Maybe the delivery driver said "hey this was sent to you". Accepting delivery of that doesn't mean you have to pay for it.
For instance, say you are a store that orders a 1/2 pallet of coke products every week. Then one week the driver leaves a full pallet by accident. Do you get that extra pallet for free? What if you forget to place the order, but the company for whatever reason sends the usual 1/2 pallet anyway? Should you have to pay for that delivery if you use it? These preexisting relationships create situations different than the mystery package on the doorstep.