One thing I sort of wished was touched on a little more: the concept of country is surprisingly modern. Modern international relations theory tends to trace the concept back to the Peace of Westphalia in 1648, but honestly, even that is really too early.

The map shown of 14th century Europe is doing better than most in that recognizes that several borders (but still too few) are fuzzy rather than lines on a map. The other problem you run into is that, in most non-state societies (in the Weberian sense of "monopoly on the legitimate use of force"), political linkages tend to be fragile and based more on personal ties so that a Big Man's successor may well repudiate the alliances and homages the Big Man makes. Which makes it hard to draw maps, because is Burgundy a part of France? The Duke of Burgundy is as often as not fighting the French king.

This is what makes adjudicating the "oldest continuous republic" hard, because at what point do we say that the homages San Marino is paying stops counting as being part of that country?