WASHINGTON—I spent a good chunk of the last year and a half working on a documentary series covering contemporary Latin American history for the National Geographic Channel. It has started to air in Spanish- and Portuguese-speaking countries, and will soon air in other languages. I have been asked a few times what I learned from this experience.

I think the most important lesson was that Latin Americans don’t consider themselves Latin Americans. Despite the increased migration, trade and political connections among countries of the region, most citizens are unaware of the recent and not-so-recent histories of their neighboring countries.

Which is why so many nations keep repeating the mistakes of the past—and why in those countries that seem to be on the right track, the forces pushing in the opposite direction are so powerful.

Venezuela would not be in the grips of a megalomaniac populist if its citizens had a greater understanding of what populism did to Argentina or Peru. Bolivians would not be perennially on the verge of civil war if they were more aware of what became of the Mexican revolution—a seven-decade dictatorship—once its ethnic-and class-based politics displaced the liberal spirits. Argentines would not have built an economic model based on commodity exports if they had a better idea of what happened to their neighboring countries once the export booms of the 1920s, 50s’ and 70s’ subsided and states were left with overwhelming spending commitments.

The scant awareness of one another’s history is compounded by a lack of information on the part of young Latin Americans of what earlier generations of their countrymen went through. The old demons—abuse of power, social and ethnic resentment, the constant rewriting of constitutions, inflation and nationalizations—are back in part because older generations failed to pass on the hard truths to younger ones. It struck me, as I talked to peasants in Bolivia and Mexico, to professionals in Brazil and Argentina, to small-businessmen and women in Panama, to students in Venezuela or Peru, and to presidents everywhere, that Latin Americans are much better at preserving political memory when they migrate than when they remain in their countries.

No one who follows Cubans or Mexicans in the United States, whatever their economic condition, can fail to notice how the older generations inculcate in the new ones a love of things they found hard to obtain or practice at home. This is probably why Cuban-Americans are so profoundly committed to Cuban freedom even if they have no personal recollection of living on the island. And this is probably why Mexicans in the United States are more interested in jobs than in living off the welfare state—whereas back home movements based on the idea of wealth redistribution have a huge following.

There have been marked improvements in the region, from Mexico to Argentina to Peru. About 15 million households ceased to be poor and became lower middle class between 2002 and 2006. Unlike the middle class that emerged in the 1940s through the 70s’, which was related to the rise of the bureaucracy, the new middle class is linked to enterprise—partly to small businesses that serve consumers or provide services to bigger corporations. But this is in great part due to the reluctant and unpopular acceptance of some governments of the need to open up their economies, not yet a testament to a cultural shift.

My travels confirmed that, unlike almost every other region of the world, Latin America is split down the middle between those who think their identity can only be expressed in confrontation with the outside world and those who are eager to play in the big leagues of economic development. Latin America is caught between two diametrically opposing forces seeking to determine its course for generations to come—a momentous struggle between modernizers and reactionaries.

If the modernizers are to have the upper hand and take the continent to a place of no return, the flaws I have mentioned will need to be overcome. Brazilians, Mexicans, Argentines, Colombians, Peruvians, Venezuelans and the rest will need to have a much better understanding of the lessons of their neighbors and of the need to pass on their experience to the next generation. Latin Americans will need to rediscover themselves.