If the Vikings stayed in America and America was known about by Europe hundreds of years before Columbus. Would there be a sort of Scramble for America? Would there be meeting by European nations like the Berlin conference to divide America between the European nations? Who would win and who would lose out? If the geography was not known about, such as the Mississippi river or Appalachian Mountains, then some nations may unwittingly get good or terrible land. How this affect European colonisation of America? How would America be today? What you think?
America was sort of known to europe before Columbus, there had been rumors of a land to the west due to the viking expeditions.
There WAS a “scramble for america” in OTL, with various european powers trying to extend their influence upon the continent, it merely occured more slowly and indirectly than Africa’s due to technological and societal differences.
There WAS a “berlin conference”, the treaty of tordesillas, and while an ATL division could include more powers, the church is still likely to get involved. And it is still unlikely to be as abrangent as the Berlin Conference due to societal and technological differences between the periods.
Your WI seems to be based on the vikings staying on america and butterflies developong from that, but a lot of your later ‘would?’ are thing that kind of did happen OTL, and are unlikely to happen in a more similar way to Africa because europe is far too different between the 15th and 19th century.
In regards to your last few questions, well, honestly, almost anything is plausible depending on how colonization changes, so the ‘how the americas would change’ is entirely dependent on the author.