What's there to trade with the Americas? There's no gold in northern Canada, and I can't seem them sustaining it long enough to establish firm trading contacts in Mesoamerica and create secure trade routes from Central America to Vinland and then to Europe.
Well, if the Norse got there first, then I'd say timber would be an important export, especially with Iceland, what with it's scarcity of trees (thats why many of the houses there were partially built underground).
Also, theres the fur trade. The fur coming from beavers and maybe even bison hide all the way from the Midwest.
In exchange, the Norse colonists in America would require livestock, especially horses, cattle and sheep. And very probably iron ore as well, although it wouldn't be to long before the find sources of iron ore in North America.