Honestly I think the most common practice is to simply copy the countries from the IMDB You have something like Harry Potter which is produced by Warner Bros but is listed as a UK US film Dr Zhivago is also an MGM production but was listed solely as a UK film although I removed that yesterday since there is no agreement among the sources on what nationality that film is I think generally it s probably not wise to follow precedents on other articles in which case we would still ironically end up with a UK US listing by just copying the IMDB countries because they all have different standards of editing I much prefer the alternative solution put forward in saying what is American about it and what is British it feels much more encyclopedic to me