The Mississippi can take BIG barges, and the short canal at Chicago allows loads to go from the Great Lakes to the Gulf, and from there to the rest of the world.
The Red River is shallow. You can run shallow barges (like the old shallow draft steamboats), but I don't think you can run much more than that. I suspect the Minnesota River (that's the connexion to the Mississippi it'd use, right?) isn't much better for chunks of its length.
Then, that just gets you to Lake Winnipeg. You'd have to do more canal building/river work through the hard rock of the Precambrian Shield to get to Hudsons Bay (the ocean), and THEN that's only useful a couple of months a year.
In an ATL where OTL's Canadian Prairies are part of the US, such works on the Red would make a LOT of sense. OTL, not so much.