I run an airline named Air Pacific, based in Guam, in History and the Future. I want to open a base in Pago Pago (Yes, I'm aware it's tiny, but there are ~30 pax routes to nearby islands like Fiji and Samoa I'd like to fill). When I open the menu to view the base airport options, only Guam and mainland US airports are available. I can't even see an airport such as Saipan on the list, even though it's less than 100 miles from Guam. I don't know why I can't see any US territories' airports. I'd really like to see this changed.
At least for the US and its dependencies, it has always been like that: when based in an overseas territory, you can only base in the mainland or in other airports of your own territory. It's not a question of distance, Saipan is just in the Northern Marianna Islands -> different.
Better add that in the "feature request" section of the forum.