OK, to expand on my previous post (tablet keyboard doesn't make for great detail) some possible divergence points, in chronological order, are:
1. In 1872 the effects of the horse 'flu outbreak was longer lasting and more widespread. Armound 97% of horses and mules are infected and 3% die.
Given the reliance on animal power the effect on travel and transport was enormous, and catastrophic. Huge backups in freight occurred all over the US and Canada; even canals (which employed horses to pull barges) and some railways (where horse transport delivered coal) were idle. A fire in Boston (the most destructive in the city’s history, destroying 26 hectares and killing at least thirty people) was exacerbated by the lack of horses to pull the fire-fighting appliances. The US Cavalry became infantry. The US government effectively shut down. Cities suffered shortages of everything from milk to coal, bread to beer and rubbish piled up in the streets.
The outbreak began in Ontario in early October and spread rapidly reaching Detroit on the 10th, New York and Boston on the 22nd, Chicago on the 23rd, Washington on the 28th, New Orleans on the 27th of November and Havana on the 7th of December.
2. On 09MAY1873 the Vienna Stock Exchange crashed, starting of the
‘Panic of ‘73’ and leading to what was known as the ‘Long Depression’, the worst period of economic disruption until the 1930s. But it could have been worse...
There were a wide array of factors behind the crash, the problems in Vienna were merely a symptom of a far wider malaise; the fall in silver prices, enormous share speculation, the opening of the Suez canal (which disrupted trade patterns), bank failures in the USA, the after-effects of the Franco-Prussian War, the Credit Mobilier fraud, Grant's deflationary monetary policy and general economic shifts all contributed to the troubles, which would last for years.
The effects are equally widespread, from the Land War in Ireland to the revival of colonialism, from the labour troubles in the USA (including the first nationwide strike, of railway workers) to improvements in industrial processes.
3. Then there is the 1872 elections in the US states of Arkansas and Louisiana (and to a lesser extent Alabama). All three states saw violence and vote fraud. In Alabama two rival state legislatures claimed to have been elected, and each sent it's own senator to Washington (in Ye Olde Days that's how US Senators were elected). The Republican controlled Senate seated the Republican legislature's candidate (almost certainly illegally). The situation was resolved by the threatened deployment of Federal troops.
In Arkansas and Louisiana things were far worse. In both states the elections for US President, Governor and state legislature were disputed, with violent clashes commonplace. In Louisiana two men claimed to have been elected governor (Kellogg and McEnery). After clashes, including the Colfax Massacre (a clash around the fortified county courthouse where many blacks had taken refuge) which left more than 150 dead, Grant deployed Federal troops and supported William Kellogg.
In Arkansas the situation became known the
Brooks-Baxter war, and gradually escalated until 1874 with both sides (Elisha Baxter and Joseph Brooks) raising troops and fighting a low level civil war, in addition to racially motivated violence by former Confederates. The 'war' left 200-300 dead and the racial violence killed as many.
4. Next there's the Great Upheaval,otherwise the ‘
Great Railroad Strike of 1877’, which began on 14 July 1877 in the West Virginia town of Martinsburg and lasted about six weeks. Rioting and civil unrest were widespread, mainly triggered by wage cuts, the general economic depression (see point 2 above) and the disputed election of 1876 (it's a bit of a theme running through the period).
Pitched battles were fought in several cities and towns, between strikers and police, vigilantes, private guards, state militia and Federal troops (though in several cases police and militia refused to fire on strikers). Hundreds were killed, many (if not most)of them unarmed.
Workers in St. Louis briefly established a Communist government before troops were deployed.
5. Finally there's another plague, Yellow Jack. The 1878 the Mississippi river valley outbreak of outbreak of Yellow Fever.
Tens of thousands of people fled the cities of New Orleans, Vicksburg, and Memphis, perhaps 120,000 were infected and about 20,000 died. Another outbreak in Memphis killed about 5,000 people. The plague devastated Mississippi, both socially and economically, with entire families killed and thousands fleeing. Quarantine regulations ended trade and travel. Some entire towns, for example Beechland, near Vicksburg, were abandoned completely, becoming ghost towns because of the epidemic.
Historically this was a serious outbreak, but relatively geographically limited in scope. What if it had spread further?
If you really want to screw the US, worsen all five of these events. For example;
1. A worse strain of horse 'flu that kills 30% of those infected and leaves the survivors weak for months.
2. A worse economic malaise.
3. Poorly handled Federal intervention with more clashes with local anti-Reconstruction elements triggering a low-level guerilla war across the former Confederacy.
4. Longer lasting and more violent labour clashes.
5. Widespread yellow fever epidemic.