It would certainly take a shift in their focus and I doubt they could colonize on a large scale. However, they did have some significant seafaring capability and some of them (as the vikings) even had some history of going to some of those areas.
They might, for instance, put colonies in what's now Newfoundland, Labrador, Nova Scotia, New Brunswick, and maybe even Quebec and Maine. If these are sizable and stable enough, that might shift some later French/English settlement.
It could also breath new life into the Greenland colony, and Scandinavia could in theory send a high proportion of settlers relative to population.
Why does everyone think 100 years is enough time to recover from diseases? Perhaps just smallpox... but youre talking smallpox and everything else imaginable except perhaps syphilis already was already present. Plus the pressures of ecology changes and conquerers with still slightly better weapons. Hard to get busy repopulating when you're also fighting for your life and dealing with learning how to adjust to new ways of life with horses and white man coming in killing beavers and introducing invasive species taking good land, etc. I dont think 100 years changes much if the amount of white (and more importantly black) people come over as per otl. Remember malaria didnt exist in America, so as soon as Europeans and Africans bring it over you will see entire ecological zones become inhabitable which used to be considered paradise.
It's not, as evidenced by the huge amount of epidemics that regularly killed 25%-50% of entire tribes into the 1700s and beyond. We probably can't even grasp the whole scale of it since records are so sparse for North America pre-1700 (and East Coast/New Mexico pre-1600). And I don't buy for a second it was just Europeans
Then the settled cultures in Mesoamerica/Andes, well, we're talking a plague worse than the Black Death in Europe, we're talking something that is utter apocalypse. And it'll keep coming back, again, and again, and again, and each time it'll be almost as bad until it isn't. And that's just smallpox!
I don't think it will make any difference, honestly. The initial expeditions that resulted in conquest were all over the place, quality and equipment wise. Medieval expeditions will be the same. Some professionals, some knights, most of the rest sailors or servants. The gap in equipment is still huge.
The major disadvantages earlier conquerors have are 1. worse ships more vulnerable to tricky navigation and also slower to make the crossing to Europe and...yeah, that's it really. I am sure they will carry early gonnes for forts and ships anyway.
Smaller than cannons, slightly less noisy, less likely to kill (compare being shot to being blown into bits). So still a disadvantage on the defensive when defending forts.