I was criticized for being anti diffusion. I actually believe that lots of European ideas got to America by boat. I also suspect information and people also went the other way across the Atlantic. I do not trust the genetic analysis comparing Indians with Europeans because the standard results appear to change every time archaeological orthodoxy shifts. Same seems to be true of linguistic analysis. They are interesting techniques but I don't trust the results.
That being said, I think that any Europeans that got here before Columbus rapidly became American Indians or died out. So the story of our landscape again becomes a story about how the Indians modified it. Although the European contacts do become part of that history and although it is fascinating how conventional academics ignore the obvious evidence for European diffusion, still in the end there is not that much more to it. I do believe that ideas developed independently here in America. So you still have to understand the stone structures and try to find out about who built them and why.