There’s nothing in the editor constraining the geographical deployment of units in Command. If I want to put ten airfields full of B-52s in Bulgaria, I can do that. But even if there aren’t hard-coded restrictions on units in Command, there’s a lot of factors that push scenarios to specific areas.
The two biggest factors are:
-Objectives. Unless it’s an open-ocean scenario (more on that later), it will be focused around the objective. So if the objective is in one country, then that’s where the scenario will have to take place. Of course, the objective could be ships at sea, in which case it’s the waters they could conceivably be in.
-Capabilities. The US Navy deploying carriers around the world is quite different from two small nations participating in a war with only short-ranged planes and boats at their command. So while the American carrier launching strikes against a target in Central Asia is able to be in multiple locations, the Uzbek airfield also launching strikes cannot be, with the limitations that implies.
Open-ocean battles are a unique experience. They can be thought of as either broad area-scenarios, or as scenarios whose locales are still specific, only specific in an expansive way. Open-sea scenarios change the objectives from geographical areas (i.e, gain control of the water around Iceland) to ships (i.e, either escort the convoy across the ocean safely or sink it). This is because there’s little point in just venturing out into the sea for its own sake. These game-changers and the huge areas involved give them a unique feeling of play.
Then there’s the issue of “exercise scenarios”, which involve fictional nations. Most of these take place in the nation where the exercise’s “Blue Force” originates in, understandable given Blue’s normal objective of defending itself. A few times exercises take place seemingly in random locations, whether to use a certain type of terrain or for ease on the part of the scenario creator.
So there’s nothing strange about scenarios seeming to take place in certain areas often-some areas just are important and simultaneously in the reach of the combatants. The archetypical example of this is the GIUK gap. Because it is an extremely important objective (controlling access to the Atlantic from the Russian mainland) and within the capabilities of both sides to reach (Just within range of Soviet land-based aviation and plentiful NATO bases in the UK, to saying nothing of submarines), it’s not surprising that in real life and fiction alike, it has been the center of naval strategy.