WI the North decides that they like their assumed power to rule South without sharing Senate with them, and never bother to grant readmission to southern States?
That is an interesting question, especially if the North did admit more states from the Plains and Northwest who tended to be anti-South on many cultural questions (although often even more racist towards Native Americans than the south was towards Blacks).
It is plausible that the southern landowners might accept non-readmission if they were permitted to maintain economic hegemony over the region. In that situation, they might be as repressive to black labor as they actually were, and until the US was confronted with international Communism almost no Northern whites would have cared about it. In fact, it is possible to imagine a scenario whereby the Fifteenth Amendment – not highly popular with northern whites at the time – would not have been passed in exchange for semi-permanent “territorial” government with elected legislatures but Federally appointed governors as was used in the western territories. In this situation, the US has to expand South as well as West, as as I said with power in their hands and compliant territorial governors the planters would have “redeemed” the South even without voting rights in Washington. As long as they were not losing power or status, they would have accepted this sort of control until something like the boll weevil infestation, and it is not implausible to me that with Southern governors still Federally-appointed, the boll weevil crisis would have been managed much better and Southern cotton production less affected that it actually was.
This scenario would have meant a much reduced “Great Migration” and more prosperous “Black Belt” farm sector even with only partial “home rule”. Thus, if there was a Great Depression-type economic crisis, the Southern landholders might have been more economically powerful than they were. There is the potential for poor white resentment in upcountry and Appalachian Mountain counties, since without having to enfranchise blacks it is not certain that these poor whites would have lost the franchise at a later date. Thus, if poor whites did become resentful of subordinate status locally and in the nation, we could have seen demands for readmission during a Great-Depression-type economic downturn six or seven decades after the Civil War. Given that it was at this time that “scientific racism” went out of fashion amongst the academic community, and that poor whites are often more extreme in their racism (at least rhetorically) than wealthy “Black Belt” whites were, then it’s certainly possible that the Southern states could have been readmitted under even more racist systems than Jim Crow, or that northern hostility and even envy of the rich planters would have further prolonged readmission.
Alternatively if a new group of immigrant Northerners came to own the cotton and tobacco lands of the South and were able to devise alternatives to black slavery to gain an adequate labour supply, non-readmission might not have been a problem. Most likely such a scenario would see very rapid immigration to the South from the poorest parts of Europe, because these would be the only places whose people would have been willing to work for the low wages offered on the plantations. Experience also suggests an
exceptionally protectionist trade policy would have been necessary to keep Southern cotton, tobacco and sugar cane viable against global competition that was rapidly increasing as new agricultural technology allowed the ancient soils of Brazil, Australia and sub-Saharan Africa to be farmed at much lower cost that younger soils in the rest of the Americas could be, although the South itself does have some quite ancient and weathered soils which did offer chances to use this new technology. Under this scenario, the US’ economic growth during the Gilded Age would likely have been much slower because of its inefficient agriculture – propped up by huge tariffs and potentially also by export subsidies and free coinage of silver – and industrial power would likely have shifted to Canada, which was nearby and had the skilled population to develop it.
With Canada as the globe’s great industrial and mining power, it would have attracted most of the immigrants that actually joined the US, leading to huge megalopolitan areas around Toronto, Montreal, Saint John and other eastern cities.
The question is whether working-class religiosity would have been as successful at suppressing socialist movements in “Superpower Canada” as it was in the twentieth-century United States?? On one side, many of the factors that allowed working class religiosity to be maintained at levels orders of magnitude higher than in Europe were present in Canada. Most critically there was not the mass anticlericalism there was in every European working class and even in those of South and East Asia and Latin America. On the other side, Canada never had the hierarchist traditions of the Southern States, its fishing populations are naturally secular and individuoegalitarian to a degree largely absent anywhere in the United States, and its cool climate means comparative disadvantages in agriculture can become much larger than in the hotter United States. With more of Canada in large and dense urban areas, this tendency would have intensified, and potentially led the US to rapidly industrialise at potentially severe political costs.