There is a simple reason why nations and borders exist: people are different and associate with others like them while avoiding those who are different. It is simply human nature.
Around the world, different cultures exist, yet can’t coexist in the same geographic area unless all are willing to respect the differences of others and the same system of law. When moral fundamentals differ, people disagree on what rules should be in place. Unfortunately, there is always a contingent of people who do not respect the rights of others and want to impose their values/worldview on others without compromise. When two or more contingents are unwilling to compromise and respect each other, a victor must prevail in that geographic area.
Wars and conflict generally establish borders. Geography typically comes into play (oceans, rivers, mountain ranges, etc). Geography often creates a natural defense, making it exponentially difficult for an invader to launch an offensive, thereby reducing the cost/benefit of an attack. When geography benefits the defending nation, it will likely result in a border.
Disputes are usually over what law system shall be in place or over land and resources. Conflicts end when one side has been subjugated and conquered, one group leaves or both sides run too low on people and resources and lose the will to fight any longer. When the fighting stops, lines are drawn. The borders established mark geographic boundaries to lands governed by a specific culture. You could pick any two nations that border one another and see the differences that separate the cultures.
Borders are good; they allow people to live in an environment that matches their values. Borders are established when peace is achieved. Conflict will ensue when two or more cultures exist within a border until new borders are set. A nation cannot live without boundaries and a harmonious and congruent culture. Any country with a subculture unwilling to assimilate will find itself roiled in conflict; such is the state of America today. When one side is unwilling to compromise and demands their values be the law of the land, one side must prevail. One group must be eliminated, subjugated, or expelled; such is the state of Israel in today’s world.
In decades and centuries past, vastly different cultures had their own regions of the world. With mass migration, vastly different cultures now live within the borders of many countries, creating a global collision of cultures. The stage is being set for a worldwide culture war. Any nation wishing to exclude itself from such a war must take extraordinary measures to protect its culture.
For America to have a homogenous culture, several things must happen. We must close the borders, have a moratorium on immigration until we have deported those who have entered illegally, and expel any here legally who support our enemies. Any naturalized citizen who supports enemies of the United States should have their citizenship revoked for fraudulently taking an oath of loyalty to this country. Any non-citizen here legally on a visa should be removed if they support enemies of the U.S. or our allies.
Finally, our nation’s history and the Constitution must be a primary educational value. A high school diploma must require passing an extensive exam on the Constitution and the founding of this nation. Teachers should have a penalty applied to their compensation should their students fail Constitutional tests. Our Constitution unites us as a culture, yet many high school graduates can’t pass the citizenship exam. When teaching the Constitution was a primary value in education, we had a homogenous culture of people proud to be Americans. When students aren’t taught the history of the nation and the Constitution, we end up with people who advocate tyranny. Should this continue, we will be in a violent battle for the soul of the country, and we’re nearly there.