[FrankoDelMar]

Aren’t the limits in the US you mention more accurately described as the consequences of an action rather than the action itself? For example if you suggest a person to commit suicide and they actually do it, you could be held responsible for murder/manslaughter, but if that person didn’t do anything then it’s a much less severe crime. Similarly, at what point does saying fire in a theater become illegal? Do I have to yell? How loudly do I have to yell? What if the room is empty? What if I only said it loudly enough for the people adjacent to me can hear it? Or is it not the consequence of people panicking, possibly trampling over each other is what makes it illegal rather than the speech itself?

[ethbr1]

In the case of yelling fire, the illegal action would be commiting assault and murder against another person.

When yelling fire without a compelling reason, a reasonable person would anticipate everyone else's standard reaction, and that in the course of that action injury and/or death might occur.

Which is why culpability in the US depends on the speaker's intent. What if I believed I smelled smoke and yelled "Fire" because of that? But was simply wrong?

Unfortunately, intent is impossible to prove definitively, without actually peering into someone else's mind. Thus, can of worms.