I'm going to go on a small bit of crazy but:
Technically, Canada could build a border wall (fence) at the 49th parallel and have it lined with silicon solar cells lined up completely vertically (little maintenance or snow removal.) In my mind, it is definitely doable assuming the price of silicon ingots/other manufacture (sand, of which there is trillions of tons on the earth) comes down in price.
Don't say it isn't doable, because the railroads (steel, across the entire nation) is arguably 10x more difficult than building a solar fence across the nation.
https://www.popsci.com/border-wall-solar-panels
I completely disagree with Popular Science. Trumps "Solar wall" is not entirely a bad idea... I endorse it.