Or it's cultural influence. Like I said on the first page of this thread, the visions of heaven described in western culture are always what's shown in movies and other cultural things from the area. Here's a source that describes near death experiences from Hindus, and they are, no surprise, absolutely different than American ones.
Ok i'm gonna try to give you the nutshell version of my opinion on the matter without too many open ends, haha. I do agree with your mention of cultural influence...and would go as far as to say that it goes to show how much programming has been done on the human psyche. In my view, when you die, you then enter another realm of higher conscious existance...which doesnt necessarily mean its going to be the same for everyone. As we know, every person on earth creates their realities for themselves every waking moment of their lives...the law of attraction is very prevalent when getting into all this. Depending on your resonance within - including the vibration and contents of your thoughts, projections, and intentions - then becomes your reality on the perceptional exterior. Anyways, this same concept goes for the higher realms of conscious existance...however amplified to the millionth degree. Our core foundation of conscious being is centered around creation, and creating...it is the nature of our true essence in my opinion. So with that being said, its not a big deal that different people experienced different things during their NDE's. The reason anyone experiences what they do is the result of what they are consciously creating for themselves from within, for whatever reason. Nightmarish scenarios are generated due to the overall fearful/negative state of mind, thus the creation and experiencing of that perceptional reality...it is a reflection from within. This same concept is the reasoning for bad trips on psychedelic drugs.