So, a lot like our existing national conversation?

Honest question: what keeps the present private-for-profit social media platforms from falling in the same pit?

It's not clear that the government is legally able to censor all types of spam. If the spam is commercial, the Central Hudson four-pronged test on commercial speech restrictions applies,[1] which requires, among other things, that the restrictions be "no more extensive than necessary to serve [the government's] interest". Non-commercial forms of spam would probably be protected from removal by the First Amendment, unless, perhaps, they overloaded the government's servers.

Trolling categorised as "obscene" would be removable, but otherwise may be protected by the First Amendment. Also, the fact that every content moderation decision may be subject to litigation would make it extremely difficult for the government to meaningfully moderate content.

Private platforms, not bound by the First Amendment, and allowed to moderate without assuming liability by Section 230, wouldn't suffer these problems

[1]: Via White Buffalo v. UT Austin

The difference is they could require proof of identity and American citizenship to be able to access the site, and the site itself could have rules that are enforceable to limit human generated spam without violating the first amendment. They would not be helpless to moderate the site just because of the first amendment, they would just need to pass moderation clauses for the site before going live with it.

In a similar vein with the fact that it's illegal to yell out "FIRE!" in a crowded theater unless there is actually a fire, they could make it illegal to advertise private businesses and make posters directly legally responsible for what they post.

If this does come about though, I hope they prohibit businesses and "Media Groups" or whatever from creating accounts or at least lock them into a walled garden that you have to voluntarily enter, segregating them from the general populace.

Those profits incentivize them to keep spam off their networks. The only incentive US Gov entities have is keeping their contracts alive and the money flowing in without ever needing to turn a profit.

Don't they? FB is full of anti-vaxxer and foreign propoganda as it is and trolling is legion. The only reason spam is partially dealt with (commercial spam at least) is because FB (and similar networks) don't want spammers to shoulder in on their profit center.

That seems fine, as long as I can just not subscribe to them.