I do agree with the statement that nations are tribal forms. City states and the more advanced modern nations alike are just a more developed form of tribal formations. We are tribal in our nature, as we are just another herd animal. Its in our nature. We have no choice really. We have to form communities in some form. The Nation is the present tribe we belong to.
On macro level that is. On the multiple levels of group membership we belong to, we do belong to different sub-levels of tribes if you will – groups of diverse cultural identity – micro levels or tribal identities, as belonging to a linguistic group, speaking a specific dialect, belonging to a faith or political movement. The Nation is just another aspect of it. Not by itself natural formed order of things, but the present manifestation of our need to form organized groups we belong to.
That is to say that in the future the Nation might not exist, but will be replaced as a phenomena by other forms of macro level organization. But still, as long as we are what we are, we will always belong to tribes.