At some point I saw a documentary where this was discussed. I don't have TV so it's either been several years or I saw it at someone else's house. I had forgotten but intended to dig into that. As I recall the program was focused on unexplained archeological artifacts in different areas of the US and Canada. The Wales connection piqued my interest. IIRC the others were thought to be more Norse/Viking origins but in interior parts of the continent.
There are a lot of interesting claims out there. Some of them seem rather far fetched but others, such as the Norse Vikings, are pretty much proven IMO. The only question regarding the Norse settlements of North America are how extensive were they? and how far south did they go?