One of the things I'm aiming to do on Alternate Mondays is to point to good AH blogs, or better yet, good "AH ore" blogs, full of the raw vein you can dig out and process into refined alternium. One of the best of those latter types is pauldrye's blog, Passing Strangeness. (Paul has also written a goodly number of goodly alternate histories in the GURPS Infinite Worlds setting for various iterations of Pyramid.)
For this Alternate Monday, our assigned reading is his entry "The Empire of the Calabash." Highlights for those of you who refuse to click: King Kalakaua of Hawai'i (r. 1874-1891) attempted to get Hawai'i (I'm spelling it thuswise to distinguish it from the State of Hawaii) some strategic breathing room during the colonial Light Egg-White Only Scramble For The Pacific by a) pursuing alliances and eventual confederation with the Kingdom of Samoa, and if that had worked out, Tonga, and eventually all the remaining independent Pacific kingdoms; and b) a "Union and Federation of Asiatic Nations and Sovereigns" with the Meiji Emperor of Japan. In OTL, the Japanese still comprehended the differential between eyes and stomach, and turned Kalakaua down in 1881; the Malietoa Leaupepe of Samoa signed up for a confederation with Hawai'i in 1887 but got overthrown by the Germans for his trouble.
But what if ...
Our point of divergence is this: the Japanese see the potential of dominating cross-Pacific trade in an instant, and sign on. The British, happy to see someone blocking the Americans and the Germans in the Pacific, provide a solid Great Power backing for the deal, anticipating OTL's Anglo-Japanese alliance by 20 years. The Hawai'ians snap up Samoa, Tonga, and (based on a farcical 1857 annexation of the islet of Sikaiana by Kamehameha IV) eventually the Solomon Islands; the Japanese back the Hawai'ian monarchy against their sugar-planting opponents (much to the anti-annexationist Grover Cleveland's delight); the British back the Japanese. This takes us up to 1897, when the expansionist William McKinley becomes President, and Alfred Thayer Mahan's theories of sea power become dominant in American policy circles.
Now, things can get screwy. The Spanish-American War goes off on schedule, but do the Americans (without the Hawaiian Protectorate-and-Annexation of OTL) have the strategic wherewithal to insist on controlling the Philippines? Or do Britain and Japan jointly guarantee Aguinaldo's Republic?
Do increasing tensions over the Pacific spill into a war between an overconfident America and a cautious (but still overwhelming-at-sea) Britain, as almost happened in OTL over the Venezuelan border crisis of 1895, of all things? (And if that war breaks out in 1895, does that push the Spanish-American War back, or cancel it until 1941?) Such a war doesn't end well for America at sea, although we might well have busted off a chunk or two of Canada into puppet states -- Quebec, perhaps, Nova Scotia or no-longer-British Columbia if we were really on the ball. Or does this crisis tie into the Sino-Japanese War (1894-1895) and now we've got a Pacific War on our hands -- which we still lose. (Either way, the war probably costs us Midway Island, annexed in 1867 for the rich, tasty guano it holds. Held. Whatevs.)
Or do we pick on the Japanese during the Russo-Japanese War, Teddy R. pushing our luck all the way to the edge of belligerency? Another demarche from the British, another threatened invasion of rump Canada, more ill feeling.
This then maybe tilts the balance against U.S. intervention in World War I, during which the Japanese-Hawai'ian Union swallows up the German colonies in New Guinea and the Western Pacific (assuming they hadn't already). But without America coming in, the Germans may very well win and take all of it back with interest.
Now we have a sullen, resentful Japan, mad at Germany and America, militarizing itself and increasingly dominating its Hawai'ian partner. Does Japan go to war with Germany as the Kaiserreich weakens? Or knock out the only fleet in the Pacific capable of stopping it: the U.S. Pacific Fleet, based in San Francisco Bay.
Or we have America and Britain avoiding war in 1895, WWI as Big Japanese Win, and now Yamamoto's gassing the carriers up from Pearl Harbor ready for the beheading strike against the U.S. Pacific Fleet, based in San Francisco Bay. If they don't block the Panama Canal with sabotage or a second carrier strike (remember, all the stuff that hit the Philippines in OTL can be re-tasked) they will soon.
Does the extra moat's worth of islands keep Japan in play long enough for F-Go to give them the Bomb and a stalemate? (Strategically, the U.S. is in a pickle, even if we can probably provide enough land-based air cover to keep the shipyards on the West Coast working.) Or do they squander their advantages on an invasion of Australia (apparently seriously considered in OTL) or Alaska? Do they try to bring Mexico in with another Zimmerman Telegram? (Much, obviously, also depends on this TL's Stalin and his appetite for Manchuria and/or destruction.) It's not absolutely utterly unpossible (although it's not bloody likely) that the Japanese can fight to a stalemate in this TL, perhaps with American Marines occupying an increasingly restive and bloody Hawai'i and Samoa under puppet governments, and everyone gearing up for the big rematch we all know is coming in the 1960s -- this time with nukes.