Belize is a democratic sovereign state that is part of the British Commonwealth, and the northernmost Central American nation. Belize has a diverse society, comprising many cultures and languages. Although Kriol and Spanish are spoken among the population, Belize is the only country in Central America where English is the official language. Belize is bordered by Mexico to its north, by Guatemala to its south and west, and by the Caribbean Sea to the east.
While Belize was the site of conflict between the Spanish and the English, the Spanish never colonized it. Thus, even after driving the English out in the 17th century, the English returned, and gained an adequate hold of the area.
In The Two Georges, the territory that makes up the OTL state of Belize is part of a larger Guatemala, a Holy Alliance possession. While there are any number of explanations as to how this might have happened, the novel does not discuss the matter.