SAS has round-trip flights from Los Angeles (LAX) to Copenhagen (CPH) for $448, NONSTOP. Flights November to March. Extended weekends available.
Note: Some small OTAs on Skyscanner have this for about $431. 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.
Carry on bag with a maximum weight of 18 lbs is allowed for free on SAS. You can avoid seat selection fees by accepting the randomly assigned seat at the gate. Upgrading to a higher fare class that includes a full-size carry-on bag for $28 may be cheaper than booking the discount fare with the added carry-on bag fee (for about $60).