Reservations for Eurail and InterRail pass holders traveling together

I live in the United States, have a Eurail pass and would like to make a night train reservation for the Lusitania between Lisbon and Madrid. The friend I am traveling with lives in Germany and has an InterRail pass. Unfortunately, this web site asks for the country of residence for all travelers, and the form does not include EU countries. So I am unsure how to make the reservation online. Any ideas? Is it OK to use the U.S., i.e., my country of residence, for both of us (given that we both have valid passes, even if one is Eurail and the other InterRail)?
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