When Captain whos'this built the House of Seven Gables there in Salem the colonists were still shipping in NAILS from Europe.
I would imagine the smithy in Newfoundland was really popular until they ran out of stuff ~
Remember, these Vikings didn't have a great storehouse of iron mine lore to depend on. Even when DeSoto visited the MidWest he stopped at Terre Haute and sent men with wagons out across the countryside to the West by SW to GET GOLD. They came back with some native copper and iron pyrite.
They missed the gold no more than 10 miles ~ the local Indians knew all about it, but weren't terribly interested in it, or the copper. In fact, the Indians all the way down to Mobile KNEW about the gold site in Southern Indiana ~ but absent improved techniques they really couldn't get enough of it to do anything about, but it's pretty much the ONLY gold between Mobile and just North of Sault Ste. Marine.
The Vikings obtained most of their iron from bog ore, as did the Saxons in England - I don't know if you would consider those examples of serious iron age civilizations, but it seemed to be suffient to provide for plenty of helmets, swords, mail hauberks, etc.
Producing iron requires many specialized skills, if the Vikings did abandon western Greenland for North America, I could see how that knowledge could easily be lost in a few generations - or even more quickly with the deaths of a few key people.