We noted before how SmackDown Tag Team Champion Daniel Bryan and Kevin Owens have also turned down the trip to the Kingdom. Owens was set to face WWE Champion Kofi Kingston, but WWE brought back Dolph Ziggler as a last minute change when Owens turned the show down. Bryan previously turned down the Crown Jewel show in Saudi Arabia this past November, due to how the Saudis treat homosexuals, among other reasons.
Sami was pulled from WWE's Greatest Royal Rumble event in 2018 because he is of Syrian descent and the Saudis have had strained relations with Syria for several years now. Bryan did work Greatest Royal Rumble, but passed on Crown Jewel.
There's no official word on why Bryan, Owens and Black are not going to the Kingdom for Super ShowDown, but we will keep you updated.