"Ride like you are invisible" is a philosophy, not legal advice. As you say, it is illegal in every jurisdiction in the US that I know of to bike against traffic (baring contra-flow bike lanes, which are quite a different thing). I have been hit once in 20 years of riding cautiously (but speedily) with the flow of traffic, and that was an inattentive driver, not anything about my style of riding (I was stopped at stop sign, ironically enough).
