How long does it take to build a "great wall"? The one in China took centuries to build with the use of soldiers and forced labor i.e. slaves. Although the minimum wage is close to slavery, it will still be difficult to find a workforce to build the great Trump wall of Triumph. The use of cheap Mexican workers would seem to be a bit of an irony if they were working on the American side and got trapped there.
When the Pope said bridges should be built rather than walls we see a more positive approach given the number of refugees around the world trying to move to another country. Australia has "solved" this by imprisoning them on a Pacific island, Manus Island, its personal Alcatraz.
Perhaps the world should come out from behind its wall of well-meaning but basically indifferent approach to refugees and work to solve the dual problems of supply and demand. Why are there so many refugees from so many countries? What can be done to meet the demand for a safe refuge? This is a far more complex issue and it can't be solved by shutting the doors and building a wall.
We are not doing the right thing yet.