Here’s the thing. The character of a place can influence a person’s mood. A person’s mood or sense of comfort in his or her environment are defined by the place, then. So, it makes sense to say changing places is what changes the mood. Move from NYC to Albuquerque, for example.
But, a person can change the character of a place. New curtains, clearing clutter, painting, etc., can make a place seem like a different place. So, it makes sense to say changing the place is what changes the mood. Change the curtains in NYC, for example, or painting can make the place seem like a new environment.
Mood, then, is manufactured. Changing it may involve changing places or changing the place.