I guess where I sit is that I read TAW not as a future of humanity, but more of a alternate past in terms of cultures.
I'll try to respond to this the best I can, but I am sure I will slip up in my words.
Steampunk (to my knowledge) tends to be heavily influenced by Victorian Age England and Europe if one goes international, so that is why the protagonists are all based on the UK and generally other European nations. There are likely Steam punk stories that are based out of non-European countries, but I am not aware of any specific titles at this time.
From what I can find, Spain at the time was in decline, and was one of the poorest countries in Europe at the loss of it's colonies, and could not readily compete with the UK. The country was not able to easily develop itself to utilize it's own natural resources and fell behind on the world stage.
Can the book be read as spreading bad stereotypes about Latin American governments? I can understand that point of view, since a lot of the prejudice that can be cast against Spain can be cast against Latin America. However, I am skeptical that Jim truly had any conscious or unconscious bias against Latin America or Spain in the context of the story. I believe he drew his inspiration from the historical context of Spain in terms of culture, and so he has no intent in terms of spreading bad stereotypes or prejudice.