Probably only 1,000 miles or less of the Southern Border needs barrier, to control illegal immigration.
The first 300-400 miles on the priority list, do 80% or more of the current traffic routes.
Because of land acquisition delays in South Texas (Rio Grande Valley and Laredo Sectors) those high priority miles were late getting into construction. The RGV is now fully contracted (over 100 miles) and some segments are already under construction. Laredo is recently about half contracted (31 of 69 miles).
When those high priority miles are done in 2021, it will be a massive train wreck for illegal immigration through our Southern Border. The easy routes, through urban areas along the border will be closed, and the remaining routes will be long exposed treks, under massive new technological surveillance.
In fact, the train wreck is already starting, in the areas where the new Trump-style Super Barrier System is completing, like San Diego.
Now lets start on Canada