Buy some steam gift card for US, create a steam account in the US, redeem gift cards and buy it there. Then you can friend this account to your main account and do family share.
It should work though. I did it just 5 minutes before writing the comment.
Maybe you need a vpn? This is the only thing i additonally had when i bought this game and activated sharing with my main account. Are you sure you cant buy like a 15$ Giftcard or any equivalant amount from a third party website?
Edit: Yes you actually need a VPN to play this Game. It only needs to be on until you started steam and logged in, after that you can disable it again and it will show the game in your library. Feel free to tell me if it worked or not.
I made a new account, got gift card and bought the game. I used VPN and I activated sharing library, authorizied main account and pc. but I do not see the games shared, because Steam now filters adult only games from being shown in the shared library. I don't want to use the main account with VPN, because Steam deletes the accounts. The are now very strict with VPN, VPN is forbidden in TERMS & CONDITIONS.