In 26 years of flying to the US, no-one has ever looked at my passport on departure as crew, and as passenger only at check-in for identification purposes and to remove entry card (white) if on visa.
Just make sure you leave the entry stamped card as you depart.
In some countries (basically from the Middle-East to the Pacific) it is an issue if you arrive as pax and depart as crew or vice versa. Better hang onto a copy of gen.dec which is a holy document in some places.
