You are so mis-informed, it is sad.
Learn Chinese history before making un-informed posts.
The Great Wall is why Chinese culture survived.
The great wall kept the Chinese from having to fight border wars with the Mongols during the Ming dynasty. It allowed them to keep their farming areas producing. The mongols were a horse mobile military force, not migrants. Raiders, not migrants. What the wall did not do was stop the Manchu. Their invasion started about 1600 and they were able to take the Liaodong region despite the wall. In 1644 they were allowed through the gates in order to help expel Li Zicheng’s rebels from Beijing. They defeated these rebels and the Ming dynasty and became the rulers of China until 1912. The great wall is a good illustration when someone say the Democrats in search of voters or the Republicans in search of cheap labor, is willing to let an outside group enter your country for their political purposes, as Gen. Wu Sangui did in 1644, you are leaving yourself open to this new groups political purposes and a physical barrier is irrelevant. Constantinople, East Germany, Ming Dynasty, if the civilization hiding behind a wall is willing to protect itself it will survive, if it is not, it won’t.
In our present situation, if we make the logical pass to US citizenship and a free ride illegal immigration, then we will have illegal immigration regardless of a wall. If we make illegal immigration a pointless activity, we won’t have illegal immigration, regardless of a wall.