Hm.

History, for one, surrounding revolutions in Latin America and Mesoamerica. The Pueblo Revolt stands out in my head, too. The concept of the penal colony as dreamt up by Great Britain certainly factored in; the current state of poverty in Mexico and the generally superior-than-you behavior of the Western world...

Shadowrun and Starcrawlers gave me some of the imagery for how corporations ruling over everyone would work out, and why someone might rebel if they had the chance. History factors in here again; revolutions are most often successful when they take advantage of the mother nation's moment of weakness (England, for instance, was in HUGE debt thanks to fighting the French, which made it possible for the American colonies to successfully revolt - among other factors)... You'll notice the revolution for La Parranda happens shortly after the Earth government collapses. That's on purpose. "Strike now while we have the chance" is the idea behind that.

Borderlands 2 and other Space Western games/films/whatever also gave me the mental image for La Parranda, as did a few Western films. Once Upon a Time in Mexico is a good example.

The relatively instability of the nation and its indeterminate government comes from real world history once again. A lot of colonial nations wound up changing their governments multiple times; even the United States switched from the Articles of Confederation to the present Constitution, a Constitution which has only lasted so long because it's constantly being revised.

Yeah, history had a huge influence on me for this RP.

EDIT: Oh, and the subterranean thing? I just like subterranean cities. A lot.