During the Cold War, the US distributed maps that made the USSR and Vietnam seem larger, closer and more "menacing."

This is a practice known as cartographic propaganda. As the name implies, it is the creation of false maps with the goal of achieving a result similar to traditional propaganda- here, generally creating a feeling of fear of the Soviet Union. The difference between this and regular map distortion is really just the function. 

If a map is distorted for cartographic purpose (like a map with the north pole at the center) and makes landforms appear closer together or shaped differently as a result, it’s generally not thought of as propaganda. 

It’s only really cartographic propaganda if there is an intended political purpose behind it, and where there is no cartographic reason to make the geography appear untrue to form. One of the most frequently used means of successfully doing this was by presenting the countries of the world on a flat surface map. Whenever a map is placed on a flat surface, it becomes distorted because of the round shape of the planet. 

It’s very difficult to portray all of the geography of the world to scale in this way (this is why Antarctica sometimes looks gigantic on these maps). This distortion was utilized in cartographic propaganda to portray the USSR not to scale and make it seem much larger, without making it very obvious that it wasn’t true to size. 

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