Okay, I have a little scenario sketched out.
Let's say that the royal overthrow in 1893 goes violent, with Queen Lili'uokalani refusing to back down from the Big Five. Robert William Wilcox, leading royalist forces, manages to defeat the Honolulu Rifles in battle at several key locations on Oahu, though they manage to take control of Hawai'i Island. Spring ends with an effectual standoff between Royalist forces and the Big Five. Not wanting to endanger his reelection by supporting the obviously losing revolutionaries, American president Benjamin Harrison withdraws support from the Big Five, and, further, manages to pass the so-called Neutrality Act of 1893, forbidding American companies from trading with combatant nations. This Act is highly unpopular and is passed on a shoe string: it will leech even more votes from Harrison's already ailing campaign. Having lost the support of their only backer, the Honolulu Rifles surrender to Wilcox and are arrested.
The 1893 American election goes similar to OTL--however, James B. Weaver, Populist presidential candidate, is able to steal Montana, Wyoming, Washington, Oregon, and 1 Californian district from Harrison using a pro-annexationist platform, establishing the Populists as a serious force in American politics. Grover Cleveland still becomes the next President, with a large majority in Congress. Meanwhile, in Hawaii, the revolutionaries are dealt with harshly, most being executed and the rest being imprisoned. Wilcox's army is used to take possession of the Big Five's properties in the nation, which are promptly distributed among small farmers as a way to win back the support of the common people. The legislature, having ousted many Amero-Hawaiians, enfranchises all male Hawaiian citizens, vastly increasing suffrage and political involvement. Wilcox, using the support garnered from his success in the war, manages to force the queen to grant more power to the legislature, which he leads. He begins supporting modernization via industrial subsidies, and higher tariffs to keep Hawaiians from being exploited by European and American businesses. Hawaii, at long last, begins to slowly industrialize and modernize, with most development concentrated in O'ahu and Hawai'i.
In 1894, in the wake of the Panic of '93, the Populists win a significant minority in Congress, largely in western and central states. Further, they also begin to displace the Southern Democrats by adding a mild white-supremacist element to the mix, as well as stealing some northern industrial states from Republican candidates. Many Democrat politicos and even a few Republicans begin migrating to the Populists, seeing their own parties as a lost cause. However, the People's Party remains largely a radical leftist, agrarian party focused on the working man and the poor farmer. James B. Weaver becomes the unofficial minority leader in the Senate, while Grover Cleveland continues to head the Democrats. Cleveland's White House maintains good relations with the Kingdom of Hawaii, though it is constantly pushing for free trade between the nations. With the Populists having changed their tune from expansion into Oceania to expansion into the Caribbean, this is one of the few parts of Cleveland's policy that they do not attack, though the Republicans continue to push for annexation and intervention.
Wilcox's Hawaii continues to industrialize, and a significant Hawaiian navy and army begin to be built up. Faced with British expansionism in the Pacific, Wilcox plays a skilful political game of gaining backers in both Germany and the United States via the giving of special economic rights to American and German companies--though immigration remains limited by several legal barriers--and the raising of tariffs on Britain. Hawaii begins to turn into a major sore point between the British, Germans, and Americans, with American-British and German-British relations quickly souring. Wilcox also increases good relations and trade with Japan, wisely realizing that they are becoming a major player in the Pacific.
A major incident between the US and Britain erupts in 1896 when an American naval vessel, the USS Maine (I went there), mysteriously sinks in Nassau harbor in the Bahamas. The Republicans, Populists, and indeed, many of the Democrats push for high reparations--some even call for war--from Britain. However, Cleveland makes a major mistake and compromises with British peacemakers on a few paltry monetary and economic concessions to the US. This is a major turning point for the Democrats, as many Democrats begin fleeing to the other two parties (especially the Populists) in droves, with even seat-holders changing party allegiance. President Cleveland serves out the remainder of his term with the congress almost completely against him, and will die of a heart attack in 1897 from the increased stress. Meanwhile, in 1897, the Populists overrun the White House and Congress, with James B. Weaver becoming President (45.3% of the popular vote, and a similar percentage of the electoral vote). The Republicans also make a decent showing, though many of their votes are stolen by the remaining Democrats (Adlai Stevenson as the Democratic candidate wins 15.7% of the popular vote, while the Republican candidate, Whitelaw Reid, wins 39% of it). The Democrats are effectively finished as a majority party, though they will remain a niche party for many years to come. The Populists begin relaxing the gold standard and providing subsidies to poor farmers and small businesses, while liberally trust-busting and deliberately antagonizing the Robber Barons. Weaver's White House begins aligning itself with the German Empire, signing several secret compacts of mutual affiliation, with Hawaii trailing obediently behind. The US effectively joins the Triple Alliance of Austro-Hungary, Italy, and Germany, expanding it to the Quadruple Alliance. It is soon expanded further into the Quintuple Alliance by the joining of Hawaii. Japan becomes an effective member with the signing of the American-Japanese Alliance Treaty in 1898, preceded by the Anglo-Russian Alliance in 1898, as Britain begins to search for allies. France joins the alliance the following year, which creates the Triple Entente. Weaver and Wilhelm deliberately initiate a naval arms race with Britain in 1898 with the massive expansions of the Kaiserliche Marine and the U.S. Navy, forcing the British to respond with expansions of their own.
As 1899 ends, the world seems poised on the brink of war: who will fire the first shot?
Hmm, this makes me want to write a TL...