It is impossible to say for certain how Northern Secession, or the idea of the Northern states seceding from the United States, would have changed the course of US history. However, had it been carried out, it would likely have had significant and far-reaching effects on the country and its people.
One possible outcome is that the new country formed by the seceding Northern states could have become a major economic and industrial power, as the North was home to much of the country's industry and financial resources at the time. This could have created a more balanced distribution of power between the North and South and possibly led to a reduction in tensions between the regions.
On the other hand, the split could also have led to a continuation or escalation of the hostilities that eventually led to the Civil War. The country could have been torn apart by political, economic, and social divisions, which could have hindered its development and caused lasting damage to its social fabric.
In short, Northern Secession would have dramatically altered the trajectory of US history, and its consequences would likely have been complex and far-reaching. However, without any concrete data or evidence, it is impossible to say exactly how things would have played out.