Mind you, not everyone in Nail finds himself playing a new role. Karl Marx is still a radical political economist, Charles Dickens is still a writer, and Darwin and Wallace still formulate the theory of evolution. But people as diverse as John Dickinson, Winfield Scott, Abraham Lincoln, and James Buchanan find themselves playing different parts, some more famous and powerful than in our world, some less so. And as Sobel himself says, one of the most important figures in 19th century history is the subject of the Sobel Wiki's featured article for the week: Andrew Jackson, the founder of the United States of Mexico.
It wasn't easy for Sobel to get Jackson included in the Wilderness Walk, in which the former rebels set out in 1780 to travel overland from Virginia to Spanish Mexico. For one thing, Jackson was only thirteen years old at the time. Nevertheless, he left his home in South Carolina, hitched a ride with a Virginia family named Collingswood, and managed to survive the two-year journey.
Thirty-five years later, Jackson was second-in-command of the army sent by the State of Jefferson to intervene in the Mexican Civil War. Succeeding to command a week into the war after the death of his commanding officer, Jackson entered Mexico City in February 1817, and within four months had seized power and made himself provisional president of Mexico. Jackson then browbeat his nominal allies back in Jefferson into agreeing to a union of the two countries, and in 1821 he was elected the first president of the U.S.M.
Three six-year terms later, Jackson retires, having managed to not only hold his unlikely nation together, but built it into a continental power capable of holding its own in a decade-long war with the despised British colonies he left behind.
Now, it may strike some readers as rather far-fetched to imagine that 130,000 Jeffersonians could successfully gain and maintain control over 3,000,000 Mexicans. I'll admit that I found it far-fetched myself when I first read Sobel. And yet, FAN founder Noel Maurer, who has forgotten more Mexican history than I'm ever likely to know, found it one of the least implausible things about the U.S.M. Here's how he put it in a soc.history.what-if post ten years back:
In essence, Mexico really has no sense of nationalism during this period, and the fiscal resources of the central government are nil....A shell of a state, in other words. More of a collection of disparate local fiefdoms, riven by simmering racial conflict and rampant banditry. Not unlike OTL Mexico in 1810-20, but without the legitimacy and resources conferred by attachment to the crown.Elsewhere in that thread, Maurer noted that the settlement creating the U.S.M., as described, certainly seemed within Andrew Jackson's capacity, and that he and Carlos Yu had both independently commented that Jackson seemed to be one historical character Sobel got right.
Mexico is in chaos, the conflicts winding down from exhaustion.
Now we have those Jeffersonians, their numbers boosted to several hundred thousand by the 1820s, still notionally part of this chaotic Mexican nation. Their financial resources are even larger than their numbers, due partially to cotton, but mostly to Alexander Hamilton....
Anyway, raising an army and marching on Mexico City, with the good white people of central Mexico cheering you on, is quite possible under such circumstances.
Do note that the good white people of central Mexico are cheering the Jeffersonians on. It's more like the organized --- if de facto independent --- Anglo part of the country coming to rescue the Hispano south. An end to the crazed bad government of Morelos and the Indian mob!
... Andrew Jackson cuts a deal with the white elites in Mexico City. The result is a presidentialist government, with the credibility and the financial resources to pacify the country --- it really wouldn't take very much --- and local autonomy to satisfy the local white elites....
The good white people of Mexico City and environs are instrumental in creating this settlement. It is not imposed on them. In fact, it is more imposed on the good white people of Jefferson, who didn't quite expect a new constitution to result.