If America were an experiment in utopian capitalism, then OP's point that utopian communist experiments last longer would be wrong. But since America isn't an experiment in utopian capitalism, this is just totally irrelevant.

It was an experiment in utopian capitalism between the post civil war era and the the beginning of the Great Depression (which if you notice is when most of those worker crackdowns occurred). A feature of democracy that is separate from the economic system is that you can have peaceful revolutions which is what occurred when FDR gained power and implemented the socialist policies of The New Deal.

I’ll grant you that’s still several decades of utopian capitalism before it collapsed which is significantly better than what people might assume if they are only familiar with recent experiments like grafton nh