It isn’t just cheap and stylish living that keeps Muldoon in Mexico. Strongly opposed to the Trump administration, he admires Claudia Sheinbaum, Mexico’s leftist president, and her party, Morena. “Despite not being able to vote in this country, I consider myself a supporter of Morena, of what they’ve done for the average Mexican,” he said.

“Whenever I hear her speak, I kind of wish we could have that.”

Ever since the two nations were born, in elite settler struggles for independence from European imperial powers a few decades apart, Mexico and the United States have offered mirror images of what America might be. Both were born in bloody conquest and stained by genocide and chattel slavery. But the founders of the United States saw themselves as innocent discoverers of a new world, unburdened by the past and racing toward a limitless future. Their founding documents were built on a creed of individual rights and freedom, though not for the enslaved.

The Spanish Americans to their south, by contrast, “knew that America was a stolen continent,” as the Yale historian Greg Grandin writes in his new history of the Americas. The Constitutions of the nations they founded reflected this understanding of their inheritance, insisting on the well-being of all of society, not just the individual. “If you failed to protect both,” Grandin writes, “you would have neither.”

Both have failed to live up to the promise of their founding ideals. But until recently, history might judge the United States as the clear winner of this continental wager. It became not just the richest, most powerful nation on earth but also the unquestioned destination for the world’s most ambitious migrants. Mexico has wrestled with many struggles — crime, poverty, corruption, a stagnant economy and a very long stretch of torpid, one-party rule — that have sapped its vast potential, including its people’s. For so long, many millions of its citizens have voted with their feet, heading north in search of opportunity.

But the United States under Trump is abandoning longstanding alliances that gave it military and diplomatic strength, upending the global trade system that made it fantastically rich and barring migrants who made it diverse and innovative. Trump, it seems, wants to rewind history and take the United States backward. Mexico has a new chance to move forward.