Neo-Confederates refuse to accept that while the slave economy brought riches to the plantation owners, that success came with a price. A price that held back progress in industrialization and gave the North an advantage.
Banks in the UK invested heavily in the development of the United States. The faster pace of shipbuilding and laying rail lines in the North reflected industrialization that drove the denser population of big cities. That growth was aided by a cheaper cost of money.
“The dread of slave insurrection and civil discord,” the Cotton Supply Reporter complained, was ever present. Even the London money market reflected these concerns, as bonds for southern railroads carried higher interest than those for northern roads. “This mistrust arises,” reported the Westminster Review in 1850 “from a shrewd calculation of the dangers, in both a moral and physical sense, which hang over a state of society whose foundations are laid in injustice and violence.”
https://www.google.com/amp/s/amp.theatlantic.com/amp/article/383660/
There is likely some truth in this, because people will always favor easy money over hard, but as their own country, industrialization would have followed anyways.
Some of that Northern industrialization was paid for by Southern money and Federal Government economic favoritism for the North.
It's a lot easier to graft off expensive Big Government projects like Railroads and Canals, and it is my understanding that most of the Railroads built in the North were from various forms of government money. I saw an article the other day showing Lincoln was heavily involved (as a state legislator) in pushing state funding for the Illinois Central Railroad that nearly bankrupted the state and wasted 13 million dollars.
Most of the Southern railroads were built by private funds.