Another problem is that a large part of the Scandinavian population is made up of free-holding farmers. These are not the kind of people that emigrates to the colonies.
..on the contrary, circa 750-850 AD they were making very significant colonization attempts into Iceland and Greenland. Changing climates combined with European diseases nearly emptied Greenland ~1050.
Bjarni, son of Eirik the Red, took 2500 colonists to Greenland to further the settlement there, iirc ~800.
Free Hold farmers don't want to move - absolutely. Free Hold farmers with 10 sons? You only need 4-5 sons to pass the farm down to, and teh more you do that, the smaller the farms get. Free hold farmer sons, with no prospects, are *much* more willing to go exploring... or vikingr as the case may be
Anyone know of a united Scandinavia TL I can read through? I'm running my own TL, but Scandinavia isn't my focus, so more details/thoughts would be good.
As for countries colonizing N. America... it might be easier just to list those that wouldn't or couldn't or shouldn't.
Come to think of it, I can't think of any right off hand that couldn't if you were willing to shift a few points.
The earliest civilization would likely be the Phoenicians. Give a slight mutation to change their birthrate and deathrate, and they could literally explode across the N. Atlantic.
If you're not worried about civilization, lots of theories in OTL about the Solutrean tool culture giving rise to the Clovis culture in N. America.