Harry Turtledove's Southern War series. Where the US is considered the 'good guy' x.x
Let's see... General militarism, oppression of Canada, oppresion of the mormons, not exactly nice to its own blacks, oppression of its native Indians, invasions of Mexico, arming terrorists in Ireland...
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although it didn't invade Mexico over the course of the books.
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Militarism? Umm, I suppose, in the sense that all of Europe was militaristic in 1914.
Canada? It was an enemy power. What was it supposed to do?
The Mormons are apparently batshit insane in the Southern Victory series, so I'm not sure; although it didn't invade Mexico over the course of the books.
And Ireland, feh.