Menzies had a British naval career, and has been through the Soo Locks, but seemed untroubled by that particular problem — and I found that troubling. Obviously it would involve ships to get across the ocean, but as of now there’s no sign of a Precolumbian canal to circumvent either Niagara or the drop from Lake Superior to Lake Huron. Menzies conjured up the river in what is now Chicago flowing w instead of e, into the Mississippi.
If they used the Mississippi , then the Gulf and so on they would have started in the Bronze Age and gotten to Europe in the Iron age.
Copper would have been so yesterday. :^)