Insane deals on several nonstop routes to Europe (fall/winter): Rome, Athens, Paris, London, Dublin, Barcelona
Crazy across the board fare drops to Europe for fall/winter.
While most of Europe is now open to US travelers, please check each countries entry/vaccination requirements before booking. This website can help to find some policies, or each country's embassy website usually has up to date info.
Each route has varied dates available at these price points, so play around with the sample search. Also, keep in mind that you can usually find cheap regional fares (e.g. RyanAir) between European countries, so you can always fly into one of these destinations, and then book a cheap regional flight to another European country.