On a recent visit to San Antonio to help support an exciting new project, John Paul II Catholic High School, I had the opportunity to re-visit the Alamo, one of my favorite American historical sites, and San Fernando Cathedral, a masterpiece of Hispanic Catholic architecture and decoration. The shrine of Texas liberty and the cathedral church of the archdiocese of San Antonio are a few blocks from each other; their proximity prompts a reflection on the paradoxes of Catholic history in the New World, and the contemporary challenges facing Catholicism on both sides of the Rio Grande.

The war for Texas independence in 1835-36 and the annexation of the Republic of Texas by the United States in 1845 were preludes to the Mexican-American War of 1846-48 -- and the latter, I think most historians now agree, was a war of conquest. Yes, various corrupt Mexican governments hadn't done much to develop the upper one-third of the country. But the circumstances under which President James Knox Polk contrived to wring a declaration of war out of Congress were murky at best, and both young statesmen like Abraham Lincoln (who vigorously opposed Polk's policy) and young soldiers like Ulysses S. Grant (who distinguished himself in combat in Mexico but declared the war an unjust one in his memoirs) knew that the American cause was not without blemish, to put it mildly.

It was also, from one point of view, a war by what was a sometimes-militantly Protestant country against what had long been a deeply Catholic country. And then there was the aftermath: the argument over how to digest America's new southwestern territories widened the breach between North and South, such that, in his history of the Civil War, "Battle Cry of Freedom," James McPherson argues persuasively that the Mexican-American War's results made the great bloodletting of 1861-1865 virtually inevitable.

Yet the men who died at the Alamo (including Protestants and Lodge members like William Barret Travis, Davy Crockett, and Jim Bowie) fought and died next to Catholic Tejanos--and in so doing, made it possible for the Catholic Church in San Antonio, embodied by the magnificence of San Fernando Cathedral, to live a life of faith and service today that is as least as well-developed as any in Mexico. Some of those who fought the Texas war of independence and the Mexican-American War may have thought that they were displacing a decadent Catholic culture and making space for an energetic, freedom-loving Protestantism; it seems inconceivable that any of the victors of 1836 and 1848 imagined they were securing the conditions for vibrant Catholicism in the American southwest. But over time, that is precisely what they accomplished.

In another turn of the historical wheel, the favor is now being returned, so to speak. A man born in Mexico will become archbishop of Los Angeles next February. Another native Mexican has been appointed archbishop of San Antonio. Catholicism throughout the United States is being reinvigorated by its Hispanic members. Meanwhile, the Church in Mexico (and throughout Latin America) continues to struggle with poverty, political corruption, and the challenge of an evangelical Protestantism that seems, in some respects, better equipped to inculcate the human virtues that make better material conditions of life possible.

Catholicism has been a powerful cultural force in Mexico for almost five centuries. Today, despite a vicious 20th-century persecution by secularists and Marxists that gave the Church new martyrs like St. Cristobal Magallanes and Blessed Miguel Pro, Mexico remains a profoundly Catholic nation. Yet Mexico in 2010 is also perilously close to becoming a failed state, its northern provinces rendered almost ungovernable by a catastrophic failure of public authority in the face of drug cartels and their wars against each other and the government.

Can an increasingly Hispanic Church in the United States challenge its brethren south of the Rio Grande to stop blaming their problems on "El Norte" and to become the protagonists of their own history--and aid in that transformation? The answer to that question is the next act in the drama symbolized by the Alamo and San Fernando Cathedral.

George Weigel is Distinguished Senior Fellow of the Ethics and Public Policy Center in Washington, D.C.