The announcement trailer of Call of Duty: Advanced Warfare had a couple interesting details that oust at least two of the locations that will be included in the game, as discovered by Reddit user MagicPuma7.
In the first screenshot below you can clearly see a Greek flag, and the architecture is clearly recognizable as well.
The second screenshot shows a Nigerian flag on the right, and the sign on the background says “Keep Lagos Clean.” Lagos is the most populous city in Nigeria. The same sign appears multiple times in the trailer, probably meaning that Nigeria is one of the main locations of the game.
Of course this doesn’t necessarily mean that those will be the only locations featured in the upcoming Call of Duty title, and more will probably be revealed in the coming months.