In answer to Jim and Dave, yes, a certain (very high) percentage of the crew on NCL America ships must be American, due to the good ol' Jones Act, which Congress has not yet rescinded. Also due to Congressional action, NCL America is the only cruise line so far authorized to sail all-Hawaii cruises, without being required to include a foreign port on each itinerary. And Moeve, I think it's not just young people (though perhaps more of them than older ones) that "have no stamina." Sad to say, I think Americans in general are not used to working the long, hard hours required of a cruise ship crew, and in any case, many who do apply for those jobs do so out of some romantic notion of how much "fun" it would be to work on a cruise ship and "see the world" (or see Hawaii in this case.) They just don't realize what's involved - and if they did, NCL wouldn't have enough applicants for the jobs, I guess.
As a fellow travel agent with only 10 years experience, I am aghast that the OP didn't know some very basic things about NCL's Hawaii cruises, and was unaware of the complaints about service. Perhaps he isn't a cruise specialist? Virtually all TAs I know are aware of the complaints, though not all have had such a negative experience as he writes about.