alternatehistory.com

4 May
In response to an overture originally made in March by Kamehameha IV, the Kingdom of Hawaii becomes a formal protectorate of the British imperial crown. HMS Chesapeake is the local ship of force for now, and the HMS Lion is fitting out in Pembroke to be the nucleus of a Central Pacific station.
The Kingdom of Hawaii maintains full domestic authority, and in return for protection subordinates her foreign policy to Imperial policy - though the existing treaties the Kingdom has with other powers will be respected in most particulars.
Historians will note that the event which likely clinched the deal was when the American Lancaster was reported off Oahu - this was included in the dispatches which also carried Kamehameha's offer, and made the Admiralty press for the acquisition of the magnificent Pearl Harbour to allow better coverage. (Now they have Pearl, they are unlikely to easily give it up - indeed, plans are already drawn up for the coastal defence batteries, which are currently slated to include around forty 68-lbers in the channel, twenty facing south into the sea, and dozens of Armstrong guns. They will in the event be completed with Armstrong-Elswick heavy breechloaders - the minimum requirement is to be able to stand off attack from any two ocean-going vessels in the possession of any power.)
Also on this date, a number of troopships make landfall off the Californian coast (having reprovisioned in Hawaii in early April). The troopers carry six battalions of infantry from India (one British battalion, one Gurkha battalion, one Sikh battalion and three battalions from the Bengal army) and this force will garrison San Francisco for now - it is hoped to eventually have up to 20,000 troops from the Indian Establishment in the area, though this is largely mission creep from the Indian department as the original plan was simply to ensure bullion shipments stopped. (This has been achieved - the Union government is in dire financial straits, though not quite as bad as it could be simply because they are unable to buy anything overseas.)