is it really?

The idea that "bad behaviour is its own punishment" just isn't very realistic over the short term in which we mostly care. The idea that "Something bad was done to you, but those responsible will eventually receive criticism in historical retrospectives so that makes up for it" for example doesn't intuitively feel like /justice/.

The sort of direct consequences you envision are, frankly, unlikely. Manager X fires you, the company lacks your expertise, as a result Manager Y's team runs into a problem, their performance is poor, Manager Y gets fired. How was Manager X punished in this scenario? They weren't. The idea that large corporations somehow "learn" from individual incidents is also pretty laughable. Most lack any mechanism to do that. Whole industries lack such mechanisms. Safety critical industries had to invent, and re-invent means of institutional learning to stop millions of people from dying, they aren't something that just magically appears when you hire your tenth (or ten-thousandth) employee.

The US employment model isn't special in the sense that this problem is distributed throughout US society. Denial of the statistically measurable unfairness of the world, whether its in the form of "name it and claim it" theology, the myth of the undeserving poor, or the continued enthusiasm for "at will" employment is a problem that Americans ought to but most likely won't address as a nation and a culture.

You've alluded to closed shop practices, for what it's worth the EU forbids both "at will" and (almost all) closed shops. You are entitled to work without joining any type of union, political movement, club or society and employers are forbidden from terminating permanent employees for any reason other than redundancy (ie there will no longer exist any job for you to do) misconduct (either "gross" misconduct e.g. fighting in the workplace, or a pattern of misconduct which you were given opportunities to correct and didn't) or clearly inadequate (not just "less than we'd like") performance. Furthermore there are strict laws protecting workers from being classed as "temporary" workers or third party contractors when they are in practice permanent employees. By far the EU's biggest remaining problem is enforcement, the most abused workers tend to be from vulnerable groups that are reluctant to confront their employers or complain to the authorities.