A lasting Norse settlement on the St. Lawrence

What if Norse explorers continued south and found the farmland of the Gulf and River St. Lawrence?

The richer land would improve Vinland's chances, but distance and the need for a self-sufficient settlement would still constrain growth.

Better farmland around the Gulf and River St. Lawrence would give Norse settlers a reason to remain. An objection is that sustaining an American colony requires organization the Vikings lack. Alex answers with Iceland: large groups could establish communities from scratch using relatively simple technology, reducing dependence on regular external supplies. The objection remains that a self-sufficient colony still requires substantial organization. Iceland offers a harsher environment, while the St. Lawrence is farther from established Norse settlements, leaving a tradeoff between local resources and distance.