The airports are ghost towns on Thanksgiving day and Christmas day. International travel isn't a priority for Thanksgiving week in the US. Cannot imaging Delta or United don't have a decreased frequency in flights, international or otherwise, during Thanksgiving week. The weekend before and after Thanksgiving are nighmares, though. One of the reasons business travel ceases both holiday weeks is the business travelers don't have the patience to deal with the inexperienced travelers and avoid travel altogether.

I rather enjoy flying to Europe Thanksgiving week. The airports are a nighmare for domestic flights, but not so much so for international flights Thanksgiving week. The US version of Thanksgiving doesn't exist elsewhere in the world so no issues with competing holidays. Christmas is another story, though.