I think the overview effect is due much more to who went to space than to space itself.
The people who could go on space missions are intelligent, curious, thoughtful people because that's what it takes to achieve a spot on the ride. It makes sense that such a person might have a profound realization seeing Earth from outside.
So my answer is that even if everyone went to space, many would be unmoved or moved differently.
Those persons were already intelligent and curious, they already knew everything and they already had time to think about it. Still most (if not all) reports a change in the world vision/perception without any hidden truth revealed.
It makes them more globalist and inspire them a feeling of unification that was not there before.
I have the feeling that the info about the entangled systems on earth is already in our brains, the average person is already aware of the interdependence of the systems, but only from the theoretical point of view. Probably seeing the earth from space can trigger the the feeling of "this is real" instead of staying in the theory plane.
I think you give the average person too much credit. I you gotta think of all people from all places, cultures and educational background. There I see a lot of potential for people who would not experience this effect.
Well, I am not going to negate that I am bit over optimistic :)
But to make an example of my words I see this effect similar to the bonding effect when fathers hold their newborn babies for first time. It is an emotive and unique experience for most of them.
You saw it in an ecographie, you read about it, you may have some other kids. Still the effect is unique and long lasting.