You’re confusing the U.S. Constitution with free speech. The Constitution only protects some kinds of speech, and only for American citizens. I’m not American. Most people are not American. Surely you realise there are many others countries out there, and other kinds of speech?
You say “harmful” speech has no place in the public square. Who adjudicates that? Right now it’s Elon Musk. Are you really happy with that?