The Norse wouldn't have crossed the Atlantic to get to America, and likely wouldn't have used longships in any case to do so, at least not until the navigation was well understood. (Viking is an occupation -- raiding -- not a class of people.) Norse settlements in Greenland and later in Newfoundland were reached by island hopping west from Scandinavia to Iceland, with intermediate stops (e.g. the Faeroes) along the way; the Greenland settlement was an extension further west of the voyage from Iceland, and then the settlements in Newfoundland would have been reached down the coast from there. That's a different route entirely from Columbus' voyage west-southwest from the Azores and Canaries to get to the Caribbean.
The Norse would likely have used a trading ship, the knarr, on the initial voyages to Greenland. I wrote more about them here: