I think you over oversimplifying somewhat. Most countries have a very deep history and a long chain of events that leeds to what is now their countries and borders. There has been plenty of kings and rulers of different lands, and wars fought over said land, but again this have evolved a lot over the ages.
One idea you’re touching, that borders aren’t real can be a good one. When astronauts take their first trip to space some of them are almost overwhelmed by whats called the ‘overview effect’. Seeing earth as a blue marble, with no borders and realizing we all share this small island of life we call earth circling around the sun. In this regard it would be nice in a distant future that what country you were born into has no limits to you possibilities in life. and no one will judge you because you live on the “wrong” side of a border.