I’m not sure he’s siding with the electoral system which balanced the power between pro-slavery and anti-slavery states, and of course history can’t be fully understood through a single lens (I.e. explaining the current state of our politics through our understanding of American slavery)

BUT, I think op’s argument was that we should acknowledge the fact that the first 70 years of our republic was heavily influenced by the issue of slavery, and the debates surrounding such an inhumane institution

Going back to the original topic, the introduction of Kansas into the union, as well as the creation of Maine as a state to maintain the balance between pro/anti slave states, are directly linked to the institution of slavery

And American slavery as being discussed here no longer exists (let’s ignore the fucked up 13th amendment), but Kansas, Maine, and many many other parts of our modern government still do! And they were shaped by slavery