Karl Marx’s first big job was writing about the American Civil War. As it happened. Socialism had been around for a long time by then. Marx hadn’t written Capital yet.
In a roundabout way that I can’t really explain, this confluence of circumstances is how we got to where we are right now. We can’t talk about Karl Marx without talking about the Civil War, and we’ve spent a hundred and fifty years not talking about the Civil War (to the point of letting nonsense like Gone with the Wind through), and it’s easier to just tie this to our national belief system of Capitalism and declare Marx to be the Anti-Capitalist who therefore Must Not Be Read.
Who cares what the primary contemporary European commentator on the Civil War said? He drew economic conclusions that we didn’t like. It’s all discarded.
And therefore all European intellectual insight into our most profound crisis is banished. We don’t have to think about it.