You’re talking about post-rebellion. If the war was indeed all about economic control of the U.S. then there should have been something prior to the war indicating that, shouldn’t there? So how was the North imposing economic control over the South or vice-versa?
I look at as part of the Rebellion, not post. I am thinking of the development of canals & the rail lines, roads and regional cities.
My thoughts point to the cotton gin and the stern wheeler, along with the development of the Erie Canal and subsequent rail (and paved) roads, which follow them. Also, I think of the tit for tat of the Compromise of 1850 as just one more example of the back & forth in American politics that continues to this day. People were fed up with
This war was and is about who gets to make money off goods and how much they get to make. I think that included sources of cheap labor. I think Northerners wanted and encouraged the thought that freed slaves would be willing, cheap labor for canal and rail lines. To call slaves ‘free’ was just lip service.
My opinion anyway.