Alas the history of walls is abysmal.
The Chinese Great wall built over 2,000 years was just piles of dirt except for near Cities where it resembles a fortress, it didn't stop the Mongols or the Manchus, Han Chinese are generally made up of Mongol and Manchurian descendents, the Chinese wall was built by slaves paid for by tribute.
The true meaning of the Chinese wall was an expression of Imperial dominance that was the psychological purpose of the Great Wall of China.
In the final analysis the Chinese wall created a Walled-in view rather than a Walled-out view which caused China to scuttle it's fleet in the 15th Century deferring a feeling security to become physical isolation followed by the 100 years of humiliation.
Same with Israel's wall, the only chance Israel had to succeed was to blend in and assimilate, the wall seperating them from Palestinians added to a psychology of apartheid that will prove to be untenable.
Hadrian's wall also built 2,000 years ago was the better wall, it was really the only wall seperating Barbarians from Civilization, all others were one faction of War Lords opposed by others and not part of Civilized cognition, but Hadrian's wall was short built of stone in 6 years by 15,000 soldiers and other volunteers.
The Romans could have built a similar wall in Germany but they were not stupid, they did build one between the Danube and the Rhine which worked fine until the God dammed rivers got frozen over, that was a bad week for the Romans.
Trump is committed but should settle for an electric fence, "low voltage of course" with a quick response network when ever the system is violated, but I doubt that even then Texans will accept it for more than a few decade before pulling it down.
Alas the history of walls is abysmal. br br The C... (