Maybe. Just how developed were the Southeastern Mississippian culture people? Georgia and Carolinas? The Norse can easily enter e. g. St. Johns River from Jacksonville to beyond Palatka... if they hear of sea in the west, it will be easier to just check if the peninsula has an end. Consider the number of first settlers who did the 1000 km circumnavigation of Iceland, or Erik the Red exploring over 1000 km northwest along Greenland coast.
Regarding Hansas... when will anyone except the Vinlanders themselves develop ships suitable for trans-Atlantic trade?
The chiefdoms of the Mississippian culture sophisticated enough as they had large settlements, a hierarchical social structure and had large-scale Maize production, and were developing a diverse range of specialist crafts. But what could the Norse get in return for iron tools and domesticated animals? Perhaps they could manipulate tensions between different tribal-confederations, and profit from the local conflicts through the slave-trade?
I think Cogs, which were first developed in Flanders and the northern Netherlands, appeared as early as the late 11th century. If Iceland is going to become the middle-man in the trade between the Vinlandic Gothord and the states of northern Europe, Cogs would soon out-phase Knarrs as maritime vessels of the eastern coast of North America (although Knarrs may still feature for a long time as river-craft).