American private companies aren't forced to censor these things by the government, they are leveraging their own freedom to operate their business with respect to their own prerogatives.
The eighteenth-century ideal of free speech in a public forum has now become de-facto mediated by private companies acting in their own interest. Some may believe in free speech more rigorously than others (say Reddit, as compared to Facebook). The fact that the government cannot censor speech matters less and less nowadays, given how much speech now passes through private companies' control.
> free speech in a public forum has now become de-facto mediated by private companies acting in their own interest
This statement is misleading. Some public internet forums owned by large corporations are mediated by companies acting in their own interest. Nobody is required to use those forums and many alternative forums exist, other individuals or firms are also able to create their own online public forums subject to whatever speech standards they consider ideal.
> The fact that the government cannot censor speech matters less and less nowadays, given how much speech now passes through private companies' controls
This is not true. The fact that government cannot censor speech is as critically important today as it ever was. It doesn't matter that a lot of speech passes through private companies because that is a free choice made by individuals who voluntarily push their speech through those companies and are free to take their speech elsewhere if they desire. Additionally, censorship or moderation is sometimes a desirable feature of a social media product because unbridled free-speech is sometimes abused in a way that is antithetical to the user experience and thus to business prerogatives.
You're being disingenuous. Your assertions apply in some narrow senses, but are seemingly inapplicable to the overall situation. For most of society, webcrapps are currently the de facto town square. A clique of companies has obtained the position of censoring the vast majority of interpersonal speech, period.
But sure, there are practical angles in the US where, for example, if we could shift the popular focus to Free software, We could regain society's Freedom of Speech. Perhaps you're focused on the technicalities because you're trying to work towards that - but talk constructively rather than dismissively. It helps nobody to push a stubborn idea that there is some strict distinction between USG and the S&P 500. Whether the political bureaucracy controls corporations or corporations control bureaucracy, it's all government.
In a corporatist system of government, corporate censorship is state censorship. When there's no meaningful space between corporate power and government power, it doesn't make much difference whether the guy silencing your dissent is Mark Zuckerberg or William Barr. America most definitely has such a system.
And when independent candidates run for office and can't get their message out for being shadow banned, and the corporatist candidates are always the number one trending subject, you'll be there to finger wag for not bothering to set up their own world-class content distribution system first.
I reject the idea that ownership of one of the most popular websites in the world is comparable in power to the threat of force that underpins the legal authority of the most powerful military in the world. I think that assertion is extreme and that you need to present some strong evidence to explain why popular websites are comparable in power to the justice department.
Watch the BBC documentary Century of Self, about Edward Bernays, the founder of propaganda in the US, who learned about psychology from his uncle Sigmund Freud, and happened to be the instigator of modern marketing.
The study and control of group behavior is real. The network of educated and privileged elite is real. The power of the media run by these elite perhaps surpasses that of the justice department. The media can start wars.
It is not reasonable compare a company choosing not to host content that hurts marginalized people, with a company being forced not to host content critical of the most powerful people.
I disagree; I'd even say this is a peculiar blind spot in US political culture. Practically, it's probably easier to have a similar life in a non-US country than to have a similar life while avoiding these big platforms. Yes theoretically the US government has the ability to use violence against you while Twitter doesn't, but that doesn't seem to make a lot of difference to the practical impact - people are more worried about the government ruining their livelihood than locking them up, and that's something that Twitter can do just as well.