American Airlines, British Airways, Iberia, Finnair and various other airlines have round-trip flights from Dallas (DFW) to Zurich, Copenhagen, Oslo, or Tallinn (ZRH, CPH, OSL, TLL) for $419-$497 with a connection. Flights October to December. No Weekends. 7-day minimum stay required. No Christmas dates available.
Some small OTAs on Skyscanner and Google have this for 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.