Follow-up question: How much would the North American agricultural civilizations (Pueblos are the most relevant here, I guess) of 1415 AD actually have known about the Pacific Northwest?

Because AFAIK, the Pacific Northwest was surrounded by mostly hunter-gatherer cultures.

Not an expert, but I can tell you that ancient Mexicans considered the people to their north "Chichimecas" (lineage if the dog) as uncivilized nomads much in the same way the Han Chinese looked upon the steppe people to their north.