Cranmer was a province of the North American Union. It had been a province of Nueva España until a 19th century war, in which Britain defeated the Holy Alliance and annexed large chunks of the latter's territory.
The province was bordered by Louisiana to the east, Phoenix to the west, Missouri to the east, and the Nuevespañolan provinces of Nueva Vizcaya and Nuevo León to the south.
Cranmer takes up most of the OTL U.S. states of Texas and Oklahoma. However, both the eastern section of Texas and the southeastern portion of Oklahoma are part of Louisiana in the timeline.
The name Cranmer is mentioned nowhere in the novel proper. It is probably a reference Thomas Cranmer.