The U.S. Supreme Court appears to have decided that for something to qualify as a "true threat", it has to involve a certain degree of recklessness that it would be interpreted as a threat by a neutral bystander, or involve intent.
"The question presented is whether the First Amendment still requires proof that the defendant had some subjective understanding of the threatening nature of his statements. We hold that it does, but that a mental state of recklessness is sufficient. The State must show that the defendant consciously disregarded a substantial risk that his communications would be viewed as threatening violence."
"The question presented is whether the First Amendment still requires proof that the defendant had some subjective understanding of the threatening nature of his statements. We hold that it does, but that a mental state of recklessness is sufficient. The State must show that the defendant consciously disregarded a substantial risk that his communications would be viewed as threatening violence."