Great wall of China = 5,500 miles long
US Southern border with Mexico = 2,000 miles long
You telling me primitive chinks in cone caps built over twice the length of wall we need and did it by hand?
We have Caterpillar and other equipment manufacturers of modern earth moving equipment here.
This would not be a difficult project.
Expensive, yes but only if union labor is involved.
The solution is too easy......