Let's think for a second.
Would such a world benefit mankind? Would it destabilize the current geo-economics? Is there even a remote possibility that we as humans let go of this ancient tradition of drawing lines on sand that have only served to create problems among masses and has done NOTHING good so far?
Well there is a different prospect to this theory. Consider there are no home boundaries and everyone can go anyone house and stay there. You can understand what mess it will create and how difficult it would be to manage. So therefore we have home boundaries, then we have cities division and then countries borders so that there is a division everywhere so it could be managed easily.
You are confusing privacy with nationality. That is equivalent to saying you welcome your guest into the living room with the same vigor as you would if in your bathroom. We may own homes and land but do we own a country?
You can have cities and states and allow people to move freely between cities and states just as easily between borders. Look at the European nations.