NO. We have extradition agreements with some nations to return a criminal but not a witness. To return as a witness is voluntary as it should be. One must honor an order to appear in court in the USA if you are here in the USA. How would you feel about an order to appear in court in Iran, Cuba, Equatorial Africa, etc?
Zoom testimony and electronic transfer of the footage.
IIRC, the Hague Convention also applies to witness testimony. The couple can answer written questions and provide a copy if the recording.
Well, that is why you dont have extradition treaties with third world countries and dictatorships, what about European countries? It doesnt make sense not to be able to have some kind of reciprocal treaty to compel a witness to turn over evidence or give testimony in a trial for something that is a crime in both countries. They could even do it by video link.