So before looking further into the "legalities" of your question, did you have 3 local nights in the US and hence were you "acclimatised" or "non-acclimatised"?
Sorry - disagree
Irrelevant whether he had 1,2,3 or 20 Local Nights in the USA. For the last UK-USA sector he was "unacclimatised" due <<The crew member will remain acclimatised thereafter until a duty period finishes at a place where local time differs by more than 2 hours from that at the point of departure.>> i.e. the USA-UK leg - IMHO.
NoD