Thomas Wheaton's translation of the Mexican historian, Dr. Angela Moyano Pahissa's M xico y Estados Unidos: or genes de una relaci n, 1819-1861, asks the essential question framed in the English translation's title, Why are Mexicans and Americans so different? In seeking an answer to that question, Angela Moyano gives us a superlative historical narrative of the complex cultural, diplomatic and military conflicts involving the ever shifting border separating Mexico from the United States before the American Civil War. Such a translation is urgently needed, not only because of the recurrent tensions between the United States and Mexico in the twenty-first century but because the history is written from a Mexican perspective, a perspective of which few people in the United States are aware. The reader will obtain a new awareness of the differences between Mexico and the United States, a more objective view of the United States' role in the world, and a new appreciation of the validity and importance of cultural diversity.Culturally, the differences between Mexicans and Americans were embedded in the conflict between a predominantly Catholic people versus citizens who were predominantly Protestants. This intense and profound conflict is laid out in the first chapter of the book, where the Weber thesis is extended to the United States in the form of Manifest Destiny, where white anglo-saxon Protestant's believed that their value system embodied in the Protestant Ethic, gave North American politicians, businessmen and rough neck Jacksonian adventurers the mandate and right to occupy and annex Mexican territory. In this clash of civilizations the people of the United States assumed that it was a conflict of a superior civilization over an inferior one where resistance would be feeble and futile. Not only that, the Protestant invaders assumed that many of the Mexican people would welcome them as liberators freeing an inferior people from their backwardness, ignorance and decadent past, a recurrent theme in North American culture and government until today.The main part of Pahissa's book tells the heroic and largely untold story of the efforts of brave Mexican politicians, diplomats, ranchers, farmers and common soldiers to resist the Northern invasion and defend Mexico's original territory, which stretched as far north as the Oregon Territory and as far south as St. Augustine, Florida, the oldest city in the United States. The diplomatic efforts were remarkable at a time when Mexico's newly declared independence was seriously threatened in a period of rough and tumble geopolitics involving not only the United States but the major powers of Europe, including Spain, France and Great Britain. This fragile state of affairs was further complicated by a deep internal division between the liberal and conservative parties within Mexico itself and the the indigenous people, who were the first Americans, north and south. Equally fascinating is the related narrative of the Mexican people's military resistance from the country's regular soldiers to people militias to heroic bandits against the North American's formidable cannons and gun boats. Few Americans including Mexican Americans are aware of the scope and intensity of Mexican armed resistance of its people in defending not only their property but their rights and beliefs against the onslaught of Protestant invaders who believed that they had a superior civilization and God on their side. These little known battles and skirmishes against a technologically advanced military prevented, for example, Baja Mexico from today being part of the state of California.