Obviously bots are an issue online, and are subject to any content moderation done by social media sites. But again I pose the question, are these bots protected by the 1st amendment to say anything at all? Could legal action be done to prosecute AI written text / audio / video?

Bots are not thinking, have no emotions, and I guess would be considered an intellectual property of the AI host rather than the physical property of any one user.

So do those speech rights fall on the shoulders of the host, or the end user?

There is an argument that if a human asks an AI to generate text, and then publishes that text personally, it was used as a tool to create their intended message.

But a bot is created and left alone to largely run unmonitored. It can post thousands of times in seconds.