Hawaiians are American citizens, by virtue of Hawaii being an American state. Dictionary.com states that nationality can indicate citizenship, but can also indicate a common tradition, such as history or language. Hawaiians are therefore American by nationality but also, by another meaning of the word, a separate nation.
According to Encyclopaedia Britannica, the Hawaiian people descended from Polynesians who migrated in two waves, one around 400 A.D., the other around 900 to 1000 A.D. The Instant Hawaii website states that some Hawaiians seek the re-establishment of the Hawaiian Kingdom through a sovereignty movement, either by bringing Hawaiians under the Indian Native Rights acts or by achieving complete severance from the U.S.