Way to make friends with the TSA. ;-)

Is this actually illegal? I'm sure they'd arrest you, but could they actually charge you?

I guess if you see them try to use the USB killer, you'd be obligated to report it. Otherwise I don't think its an issue.

Regardless of what the law says, in practice, breaking TSA equipment, interfering with TSA duties and, above all else, pissing off a TSA officer are all arrestable offences.

If there’s any question about culpability, all they have to do is ask you, “Is there anything in your baggage you think we should know about?” and if you don’t disclose it then, you’re screwed.

What? You say you were never asked such a question? You say you even tried to warn them? Well I have sworn testimony from a TSA officer that says they ALWAYS ask that question, and you’re the guy who was caught carrying a piece of equipment designed for trickery and vandalism. Case dismissed.

Except that "I thought it would be fine" is a pretty reasonable answer at that point.