Turkish Airlines has round-trip flights from Atlanta (ATL) to Thessaloniki (SKG) for $699 with a connection. Flights January, February, March, September, October, and November. Departures on Monday, Tuesday, Wednesday, and Sunday. No Thanksgiving dates.
Some small OTAs on Skyscanner have this for as low as $659; which is cheaper than the airline. If you plan on booking there, beware of any site that charges a fee to cancel a ticket within the 24-hour “free” period. Use unknown booking sites at your own risk.