'Madam Secretary' is in an alternate TV dimension mainly because Keith Carradine plays the President of the United States. As any Team Toobworld member in good standing knows, the POTUS for Earth Prime-Time is always the same as the current occupant of the Oval Office. That's because too many TV shows are going to mention the name of that President. Right now it's Barack Obama, not Conrad Dalton.
I don't know which TV dimension that happens to be though. I've declared a moratorium on suggesting any show with an alternate President could be following 'The West Wing' or 'Commander-In-Chief' because, to be honest, I've lost track on how many times I've done that.
But whatever world this may be, the atlas of Africa is markedly different from that in the real world:
As you can see, the fictional nation of the Republic of West Africa (or RWA as it is called by the staff of the Secretary of State) takes up part of the lands belonging to Cameroon, Gabon, and the Republic of the Congo in Toobworld.
Whether or not it exists in Earth Prime-Time? I don't know. I'd have to see if any maps of Western Africa have been shown in other TV shows that are definitely located in the main Toobworld - like 'The Man From UNCLE' or 'Mission: Impossible'. And even then, it could always be claimed that the Republic of West Africa was formed after those episodes aired. This would apply to shows which only aired as soon as last season. It doesn't take long to carve out new countries in the world......