This is arguable. Our country is changing massively, and because of the network effect[1], social media platforms condense to only a few winners, currently mostly Facebook and Twitter I believe. This oligopoly[2] means that a handful of sites basically run what is considered the internet for most people.
In America, we have a constitutional right to free speech. If in our country, most people speak solely on one of these sites, then why shouldn't our constitutional rights extend onto them?
> that a handful of sites basically run what is considered the internet for most people.
That is the result of individual choices made by those people. That's like lamenting that a handful of musicians basically produce what is considered music for most people... So what?
Why? Consumers are not paying twitter for a product or service and use of twitter is not a necessity.