Walls separating peoples and countries may "work" for a time, but the historical record shows that eventually they all fail, or at the very least change and no longer serve the intended purpose.
Here are a few examples:
Border Walls through History
The walls of Jericho—a favorite Bible story from the OT.
Remember the spiritual—“Joshua fit the battle of Jericho…and the walls came tumbling down”?
Built to protect the city of Jericho, this famous wall is the one brought down by Joshua in the battle for Jericho. So, its intended purpose of protection failed.
Hadrian’s Wall—located in England along the border between England and Scotland, the wall was built by the Romans as both a barrier and a way to identify people coming into England, taxing them as a way to discourage immigration. The wall stood until the Roman Empire collapsed, and was then dismantled by “barbarians.”
Photo of Hadrian's Wall from website listed below
The Great Wall of China—which was really a series of walls built by various emporers. It was designed as protection to help China fight off various invaders. While the Wall benefited China in its growth in trade, it ultimately failed to keep invaders out when Genghis Khan led his army into China.
Wall Street—built in New York City as it was developing. It was intended to separate the native American peoples from the Dutch settlers. This wall did not last for long, and was dismantled. From the wall the name Wall Street was derived—and of course, is now a center in world trade and finance.
Berlin Wall—when World War II ended, the Allies divided up Europe--the Soviets controlling the eastern zone where Berlin was located, and the western zone with England, France and the United States each controlling an area. As the Cold War heated up, the western powers united into one zone, West Germany. Berlin remained still divided into an eastern and western sector. Because of its location in East Germany, Berlin became a place where people under Soviet rule could escape to the West. Thus, to stop people from going from east to west, in 1961 a wall was constructed virtually overnight to separate the eastern sector from the western sector. In 1989, caught up in democratic changes in Eastern Europe, the East German government suddenly eased restrictions, permitting families to cross from east into west. East German citizens took that as "permission" and began to “tear down the wall." With no military intervention stopping them, the wall came down.
More descriptions of various walls through history can be found on the Internet, including here: http://origins.osu.edu/connecting-history/top-ten-origins-walls
This website is the source for many of the details used above.