I am looking for an American English term for a "TV box" as a source of zombification and brain killing. Maybe "boob tube" is the right one? The shorter, the better.
Boob tube is the way to go:
boob tube, noun. Etymology: boob + tube (television); from the notion that television programming is foolish or is viewed by foolish people : TELEVISION ; especially : a television set
Boob tube also enjoys wider currency than idiot box, at least according to this Ngram: