Why on earth do we have what looks like an American team and a middle eastern team, and the same friggen voices on both sides??? I cant tell you how many times I had to stop what I was doing, shoot my teammate, then say oh...nevermind, he was American with the other teams voice. wtf?
I think the idea in sandstorm is that both teams speak the same language ( with arabic accent when they talk english ) because the combatants live in the same country or region in the middle-east.
This is a fictive war scenario where the insurgents might be local rebels or armed fighters of a warlord, while on the other hand the Security forces are the national army of this country in cooperation with some american soldiers acting as advisors and giving air support during the missions.
As a Security Soldier you can change the voice from english with arabic accent to american english voice of your own character :
Start game --> Click on Customize ---> then choose character --> head ---> voice ----> Spec Ops ( American )