If this is building on the Vinland Sagas so discover of North America is at about 1000 AD, Iceland and Greenland are waystations rather than sources of much immigration or export markets. But the Norse control Ireland, much of England & Scotland (remember 1066 is various Viking armies clashing under Alfred and William for England), Normandy in France, Denmark, Finland, the Volga River and Moscow (Rus meaning Viking) and that's far more population to draw from for emigration. Lots of warring places, pagans fleeing Catholicism, losing factions, etc...so the English and Gaels would already be coming to America as part of the Vinland emigrations along probably many from the Germanic states etc. and Bristol, Dublin, Glasgow, Calais, Copenhagen, etc. would become major embarkation ports several centuries earlier.
North America's population grew quite a bit faster than Europe's from much better nutrition (far more game meat, potatoes, corn, squash, beans, pumpkins, nuts, berries, etc....potatoes' broad adoption in Europe raised it's population 40% in a short period by addressing Vitamin C and other deficiencies along with yield, so Vinland's population should naturally increase like America's did in the 1600-1800's. A healthier place where your kids survive childhood at much greater rates, grow taller noticeably, and have endless opportunities is quite a lure for the same people who make ideal settlers in new lands.
Bubonic plague, typhus (traveling on Norwegian Ship Rats' pest), measles, chickenpox, mumps, whooping cough, syphilis, all sorts of murderous plagues beyond smallpox has a high passive survival rate in contaminated apparel even if the host is long dead. Maybe it's a more gradual wave than what the Spanish triggered but the Pilgrims survived at Plymouth because an earlier trading vessel's plague delivery had killed nearly everyone for a vast distance (hence the lone survivor Squanto's friendliness and getting already planted and cleared farmfields from the now dead locals.)
England had already used up much of it's best timber by then, the beginning of the coal barges from Newcastle's mines, and ship's timbers for long keels, tall masts, etc. have always been a long-distance trade good since the Phoenician lumberjacks started selling the giant cedar trees of Lebannon 3,500+ BCE. Ship's timbers and shipbuilding are big exports of New England's coastal forests and ports OTL from the 1600's forward. The St. Lawrence River Valley and the coasts of the Great Lakes would make a lot of sense for ship travel (and why Viking artifacts and accounts refer to them) opening up world-class copper, hematite iron ore, etc. while fitting well with the Viking's skillsets, knowledgebase, defensive measures, and dominating the competing tribes in longboats vs. canoes.
Figure the present states and provinces at least along the coasts, islands, and key rivers eventually of Southeastern Canada, New England, New York and Pennsylvania, probably Maryland and Virginia given their natural harbors, and the Great Lakes region. Until there's a road system, water travel rules and the Viking longboats' abilities to use rivers given their shallow draft would be quite a bit different for settlement and trade patterns with their cargo ships likely developing much faster and larger than OTL with the transAtlantic demands on their capacity.
Spain would probably be also-ran as it's still centuries away from fighting off Moorish control. Or it's Islamic Spain, Algerian and Moroccan ships/pirates etc. that show up within a few decades at most rather than 500 years later like 1492.
