That's what Alaska bill SB 214, sponsored by state senators Lora Reinbold and Mia Costello would do in part.
I think some restrictions on platforms' deleting posts might be constitutional (see my Social Media Platforms as Common Carriers? article, or these posts excerpted from that article): To quote Justice Breyer (from a dissenting opinion, but on a point which with the majority didn't disagree with, and which other majority opinions endorsed),
Requiring someone to host another person's speech is often a perfectly legitimate thing for the Government to do.
