Family Sharing (AppleOne) members abroad?

I am interested in purchasing/starting an AppleOne subscription for my family. Four live in California, one going to college in Ohio, and one currently living in Italy working for UN for 3 years. My understanding is that Family sharing is tied to "Country/Region" settings that are tied to Apple IDs and that all family members need to have same Country/Region. My question is about my brother living in Italy...can he set/reset his Apple ID to US while living there? He does not make purchases with his Apple ID or iphone...he just uses it as a phone and for internet as far as I know. He has a US credit card that could be listed as "payment method" in the Manage Payment setting. Would that work? We want to be able to share Apple Music and Apple TV. Appreciate any tips/info this forum can provide!