The US economic system by my eyes has changed quite a bit in 240 years. The dissolution of slavery was a pretty big milestone, for example. There's distinctly different eras defined by very different laws, such as the gilded age or the era of the train baron.

I guess if you want to call that entire 240 years "capitalism" and use that as evidence that it's, ah, more sustainable than other strategies, well that's fine, but that means free market capitalism has no mechanism preventing things like slavery or company towns. In fact it seems it continually fails to provide for anyone other than capital holders until another philosophy enters the picture, such as government regulation or worker's unions.

You say freedom requires vigilance, what's that mean? When the only way to eat was to work in a company town and scrape together barely the means to a living, everyone is vigilantly aware of how shitty the situation is, so then what? History teaches us the "and then what" is strike followed by reactionary state violence followed by bloody revolution, so there's your case history of devolution to violence.