Also: although planned over 2000 years ago, it wasn't really made by ancient Greeks. They gave up and made a road to transport ships on it instead of actually digging. Only in modern time did they actually finish the canal
My first thought was if this was remotely possible on this scale, how many things would be disrupted and changed from the water movement alone. The Panama canal has to have locks because of the ocean differences, but no way would you have locks spanning a few hundred miles across. This thing would have tides back and forth.
Assuming the river would be identical in depth and breadth to the Panama canal, if every man, woman, and child in the US picked up a shovel they would need to move 305 cubic feet of dirt each. So if we all just moved 1 cubic foot of dirt per day, we could pull this off in a year.
First I was excited thinking about South Canada and North Mexico, but unfortunately they screwed up the one opportunity in history to fix Oklahoma's awkward 'protrusion', so I can't with a clean conscience support and vote for this. Better luck next time.
I mean this is a pretty good visual representation of what they did when they built all the highways, just more spread out and the negative implications being mostly pushed off onto whoever didn't have enough political capital to resist them, i.e. minorities.