1916 Republican Victory leads to 1920 populist victory
In 1916 Hughes wins after 25,000 votes shift in California because of a massive advertising campaign that the US needs to arm in case either side wins the war and decides to do something to the US with all those experienced troops. The American public buys that, since a lot of them were once citizens of those European countries and know how their governments think.
The Germans discontinue the sub war because they know the Republicans (the 1916 Republicans, no resemblance to the 2004 version) are itching to start a war. The Republicans declare war without a causus belli over the objections of the Democrats and Populists. The US subsidizes the French and British by taking over their war debts to the US, bailing out the Morgan interests. They also institute a draft. Neither action is at all popular.
The Germans figure they're in trouble, so they offer the Russians a good peace treaty if they throw out the monarchy and go socialist, and the Russians take it. The German army heads west a year ahead of schedule. Italy is offered and signs a good treaty to gain the Tyrol, allowing the AustroHungarian troops to concentrate against the Entente armies in Salonika and occupy it. The French finally sue for peace after the collapse of the evacuation under aerial attack, and it's all over.
Both the Democrats and the Republicans are in deep shit with the American people. The Populist party candidate is a military veteran from the Spanish American war who had opposed the US entry into WWI, but had campaigned for the Republicans before the 1916 election on a rearming America basis. He gets only 40% of the vote, but that's more than enough considering that the Republicans and Democrats are mostly campaigning against each other. He also runs a lot of congressional and state legislative candidates and they get elected for the same reason. This gives him the clout to get several amendments passed.
The first amendment is to let women vote. That gives him victory in the next election. The second amendment is to let black people vote in the south. That loses him a lot of votes in the south, which goes solidly democratic, but with only 20% of the US population that doesn't count for much. The northern Democrats go Populist and give him 60% of the vote in 60% of the states.
The blacks give him their votes in the north and the south, but it's the north that counts, especially since one of the populist platform planks is limited immigration, which makes a lot of southern blacks move north for the jobs that would have been taken by immigrants. The income tax is used solely to pay off the European war bonds, and is only levied on the rich, mostly because they were the ones who got their war bonds bailed out. Not that it stops them from complaining.
The Europeans have a peace of exhaustion. No communists take power, but socialist parties are important everywhere, especially in German, France, England, Russia, Italy, and AustriaHungary. The minor powers are slowly pressured by threats of revolution with implicit support from the great powers. The borders are unchanged, and stay that way. Democracy and socialist ideology guarantee that minorities are treated decently.
Japan chose the wrong side in the war and is explicitly contained, losing the Chinese and Korea territories. They are less susceptible to socialist revolutions but are isolated diplomatically. They leave the world stage as a military power and concentrate on commercial success. Successfully.
