The only resemblance that snake bears to a copperhead is that it is also shaped like a snake. Copperheads don’t get that big or dark. Just leave him alone. He is eating your mice and other vermin for you.
Venemous snakes of the U.S. (with coral snake being the exception) all have “cat’s eye” pupils.
The can get that big and depending on time of year etc they can be dark. But the body doesn't look right nor the skin pattern. I can't see enough of the head and that is the real make or break in determination. I about stepped on a three footer in my gravel parking area of my driveway. I shot the snake after a good suspicion it was a Copperhead then myself and my dad confirmed it with closer detailed exam postmortem.
The snake I killed was bigger than any Copperhead I had seen in East Tennessee but was chunky body, shortened blunt tail, triangular head, with almost Rattler type patterns, and fangs.
The hardest poisonous snake to determine in the U.S. is a Cottonmouth. One in Arkansas will vary greatly from say one in Florida in body pattern. In that respect I'm luck. None northeast of the Cumberland Plateau.