It could be that it is our biological nature to follow some kind of herd instinct and build upon it. Whatever the reasons, a nation is a community of people working cooperatively for the mutual benefit and safety of one another. When that desire to work cooperatively with one another disappears, so too does the nation. If one was to adopt a pessimistic view of the human world, we might come to the same conclusion as Hobbes and assume that civilized society exists solely to avoid an unending state of war of one against all others. I suspect, though, that it is not that simple.
Human beings are much more complex than simple words and ideas can explain.
Undoubtedly, fear and desire for personal safety play a role in bonding us into a nation. It is more likely that the optimistic vision of human society as advanced by Locke or Rousseau is closer to the truth than the Hobbesian view. It is probable that the primary reason that we give up a portion of our natural liberty and periodically obey others is that we instinctively realize that it is ultimately in our own best interest. We have learned that the combined efforts of many can achieve results far beyond what one person can accomplish on his own. Laws, languages, and social customs exist for no other purpose than to allow us to minimize our differences and work together cooperatively for mutual benefit of all.