OP:
Jung believed that you can bring the unconscious thoughts into consciousness through dreams. And when he analyzed the dreams, the god image came up frequently. You must also understand that the god image he speaks of is very broad Including the numen and other secular gods.
This isn't to say that the christian god is found in the depth of our minds and possible pin pointed in the brain via neurotheology (pseudoscience btw). It just means that within dreams, it tends to manifest images centered around some figure.
We also know that the subconscious is the repository of all sensory information. Only the ones with an emotive response really get elevated into short term and then long term memory. If you live in a christian town, this religion will be in your subconscious then it's very likely that you'll have a dream about god and the like. If you are in an atheist town, and devoid of the concept, you may not have this god image. This hasn't been shown yet.
In my view, the brain is a pattern recognition machine and tends to reduce things into some smaller manageable forms. This is what the god concept is. To contrast this, look up J Campbell's 'hero with a thousand faces'. His monomyth or hero's journey is the similarity between 4000+ years of myth.
In the anthropological sense, the god concept is an evolved concept through ancestry. Starting with parents, then grand parents, then great grandparents, then previous generations, then ancestors, then family traditions, then culture, then god.
Context is important.