I think this is going to be a lost cause - we will have to buy passes again. I don’t even know how to get the pass on my UK main (I’ve bought all DLC to date on my US) while keeping all DLC. Will in-game silver currency bought on a UK account work on the US base game? 🤷🏾♂️🤷🏾♂️
Speaking from experience: It's the same for some DLCs. If you bought a DLC for a game from a region diffrent from your account's region (Let's say you bought a DLC for a US region game through your UK account) the DLC will download correctly but the DLC will not recognize/install your game due to region differences. Or the store page will not open at all and display that they can't list items.
TLDR: In-game currency won't work if you the account's region you bought the currency with is different from your game's region. Which is why I'm purely against microtransactions.