Saudi Arabia represnting more 50% of total GCC market so if CPA (USA) is dominant in Saudi Arabia then automatically CPA (USA) hold major market share in GCC.
Please just hold yourself..try to figure it out that where you want to stay and work after your study and then plan your study (qualification) according to that area because every area having different requirement, different preferences. Even the best in the world will not serve you on all places.
It doesn't mean that institutes with less members having less worth.
Anyways dear I am telling you a truth that the way you are trying to get information is not a proper way and you are trying to have too much which you required later on and that might hurt you.
So according to my point of view, try to concentrate on your A-level.