The argument of the book is that to understand what's truly exceptional about the United States, what's called American exceptionalism, is its relationship to Latin America. Other modern capitalist empires tended to rule over culturally and religiously distinct peoples that were in arguments over shared first premises. What was unique about the United States and its relationship with Latin America was just how familiar they were to each other. They both worshiped the same savior. They shared the same idea with Latin American elites and Latin American independence leaders that the historic mission of the new world was to redeem the old world, renew humanity, redeem humanity. That that shared exceptionalism wasn't recognized in the United States.