What is a border? (4)

Tell me, what exactly defines a national border? Is it where a group of people drew a line and claimed those across were outsiders? Is it truly a division of cultures? I want to discuss exactly what defines a border, whether it's political or something more.

When you think of the border between, say, the United States and Canada, do you think about the racial, ethnic, or cultural differences between yourselves and the Canadians? Of course not, the boundary is more of a political line created to say "we have this and you have that", there is very little separating us and them. However, consider the southern border with Mexico. This border is significantly different. In the eyes of the American, the Mexican is racially different and culturally alien. The southern border is not one of politics but one of division, to say "you are different than us, you stay on your side and we stay on ours".

An interesting border to examine is the disputed Israeli/Palestinian border. The Israeli's claim that Palestine is rightfully theirs as it was granted to them in the aftermath of WWII, however the Palestinians claim it as their homeland. In order to appease both parties, both must be given land in the area. How arbitrary can a single border be? How does one determine where to put a border like that? The Israelis were granted that land, and it was taken from the Palestinians, so both present very valid arguments. Most borders, like this one, were created through violence; a group forcefully taking land until they are either satisfied or stopped. 

Listen to the song "Borders Are..." by Serj Tankian, who you may know as the lead singer of popular metal band System of a Down. The song discusses precisely the point I am trying to get across. He defines borders as follows:

Borders are the gallows

Of our collective national egos

Subjective, lines in sand

In the water, separating everything

In today's era, what more is a border than a subjective line in sand? Sure there are borders like Israel/Palestine, defined by culture, but even there, there are plenty of Palestinians within Israeli borders and plenty of Jews within Palestinian borders, so what is really the point in it? The world today could exist and thrive without national borders, without national governments, simply as one, unified human race. Why stay so separate when we really are all the same: human beings.
Fear is the cause of separation
Backed with illicit conversations
Procured by constant condemnations
National blood-painted persuasions