I am trying to figure out if there were actual cultural, commercial and political links among the islands, and especially if there was an actual Hawaiian unified identity or this is constructed after the British intervention and alteration of the archipelago dynamics. The distances between Hawaiian islands seem to be a difficult gap to cover regularly without proper means of transportation, hence I would imagine that the degree of similitude between each Hawaiian island culture would not be very different to the one between these and any other Polynesia islands.
Yes, the islands themselves had a macro-economy, where each had their own specialties that the contributed to the inter-island economy.
Soon, entire islands began to specialize in certain skilled trades. Oʻahu became the chief kapa (tapa bark cloth) manufacturer. Maui became the chief canoe manufacturer. The island of Hawaiʻi exchanged bales of dried fish.
The distance between the islands may seem like a lot to someone who lives an inland life (such as myself). However, for Polynesians the distances involved were quite doable.
For example, the medieval-era Tu'i Tongan Empire covered a much larger area, stretching from Fiji in the west, to Niue in the east (about 1,300 km), to the Samoas in the north (about 900 km from Tonga).
The inhabited Windward Hawaiian islands are only about 750km from end to end.
Also remember that the islands were likely originally settled from the Marquesas, which are nearly 4,000 km distant. These people knew what they were doing on the open seas.
cropped from WikiPedia