What if Mexico had won the Mexican American war instead of the United States

Because it would mean having to do a lot of research into the US Army of the time in terms of the new leaders and would be a very involved timeline focusing on a period of US history which is a relative historical gap. As well as doing intensive research into the Antebellum US military and how it practically operated.
I swear someone did something a lot like it, but I can't remember what.

I think maybe the title involved birds of some sort.
 
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