The death was announced in a family statement, which said he had a degenerative brain disorder known as progressive supranuclear palsy.

Over more than six decades, Mr. Montaner became one of the most prominent voices in the Cuban diaspora with more than 25 novels and nonfiction commentary. Nearly all Mr. Montaner’s works blasted Cuba’s regime and predicted its demise, but with increasing frustration as the collapse of the Soviet Union in 1991 and Castro’s death in 2016 failed to bring sweeping changes in Cuba.

Mr. Montaner’s views found wider audiences with media roles including political analyst for CNN’s Spanish-language channel and columnist for the Miami Herald and its sister newspaper, El Nuevo Herald. He often struck a hectoring tone that resonated with hard-line Cuban exiles but drew criticism from others as stuck in Cold War-era simplicity.

He portrayed leftist leaders and their ideology in Latin America as obstacles to progress. At the same time, Mr. Montaner extolled American-style capitalism and Western political systems — including the 1976 book “200 Años de Gringos” (as “200 Years of Gringos,” 1983) that compared the United States and Latin America over two centuries — but widely overlooked the abuses of many U.S.-backed governments in the region.

“There is a secret family of victims of totalitarianism, which can be the families in Burma or the victims in North Korea or in Iran or in Cuba,” he said in a 2011 interview with the George W. Bush Presidential Center. “We feel a special bond with them because we belong to the same family.”

After the fall of the Berlin Wall in 1989, Mr. Montaner helped forge a political front from Madrid amid hopes that the unraveling Eastern Bloc and Soviet Union would have ripples in Cuba. While Miami-based opposition factions generally pushed for tighter U.S.-led sanctions on Cuba, Mr. Montaner favored dialogue through his group, the Cuban Democratic Platform.

In 1990, a former Spanish prime minister, Adolfo Suárez, met with Castro on behalf of Mr. Montaner’s coalition. Castro was polite but offered no concessions. “We thought, no doubt naively, that Fidel Castro would admit the uselessness of sustaining a failed, collectivist, one-party dictatorship,” Mr. Montaner wrote in a 2014 column in the Miami Herald.

As the teenager in Havana, Mr. Montaner and his family celebrated Castro’s overthrow, the U.S.-backed government of President Fulgencio Batista, believing the revolution would free the economy from the grip of Batista’s cronies.

Castro’s embrace of Marxism and violent purges by his supporters turned Mr. Montaner into an anti-Castro rebel with a student guerrilla group. Mr. Montaner was captured and sentenced to 20 years in prison in 1960. He managed to slip away from a detention camp and seek refuge in the Honduran Embassy. On Sept. 8, 1961, he was placed aboard a flight and reached Miami.

“I sang the national anthem,” Mr. Montaner told the German magazine Der Spiegel in 2008, “and was sure that I would quickly return to a free Cuba.”

Mr. Montaner’s fiction often carried a sense of a lost homeland and heartbreaking choices. In 1972’s “Perro Mundo” (published in 1985 as “Dog World”), a character chooses death over submitting to a system that would turn him into “an animal.” Mr. Montaner’s 2012 tale, “Otra Vez Adios” (“Goodbye Again”), described a Jewish portrait painter who fled Nazi Germany for Cuba and then was uprooted again to leave Castro’s Cuba for New York.

In 1999’s “Viaje al Corazón de Cuba” (“Journey to the Heart of Cuba,” 2001), Mr. Montaner tried to delve into the mind of his arch-nemesis. Castro is portrayed as a narcissistic overlord who cares for nothing but power. “Montaner’s unequivocal approval of capitalism … his categorical attack on communism (undifferentiated from Castroism) and his failure to acknowledge his own justifiable subjectivity call into question his overall perspicacity and reliability,” a review in Publisher’s Weekly said.

Mr. Montaner’s provocative style also brought public backlash at times.

Puerto Rican groups staged protests in 1990 after comments decried as sexist and offensive by Mr. Montaner on the Univision news show “Portada.” Mr. Montaner said “thousands” of Puerto Rican women on the U.S. mainland “try to escape poverty through welfare” or by having children with partners who later abandon the family.

Mr. Montaner apologized for “clumsy” remarks. Univision did not cut him from the show as protesters demanded, but the New York-based newspaper El Diario La Prensa dropped him as a columnist.

A 1996 book, “Manual del Perfecto Idiota Latinoamericano” (issued in 2001 as “Guide to the Perfect Latin American Idiot”), was decried in many leftist circles as a neoconservative screed. Mr. Montaner and his co-authors — Colombian journalist Plinio Apuleyo Mendoza and Peruvian writer Álvaro Vargas Llosa, son of Nobel laureate author Mario Vargas Llosa — argued that many Latin American leaders and societies were mired in victimhood and wrongly blame the United States and others for underdevelopment and economic problems.

In Argentina, outrage flared over the book’s slash-and-burn treatment of former president Juan Perón, saying his influence on the country should be removed “with a sharp scalpel.” Many Mexicans were aghast with the authors’ contention that calling revolutionary hero Pancho Villa a statesman was like “saying that Attila the Hun was a manicurist.” (The trio published the “El Regreso del Idiota,” or “The Return of the Idiot,” in 2007.)

Mr. Montaner said the book was intended as shock therapy against the so-called “dependency theory,” which asserts that Latin American economies were built as puppets of the North.

This was part of Castro’s mystique, Mr. Montaner conceded. “I think Fidel Castro awakens a deep anthropological curiosity,” Mr. Montaner once said in a rare comment on Castro’s appeal. “He’s the bearded man dressed in military costume with a heroic history, and he militarily defeated a dictatorship.”

Carlos Alberto Montaner Suris was born April 3, 1943, in Havana. His father was a journalist for Bohemia magazine and was an early supporter of Castro. His mother was a teacher.

After fleeing Cuba, Mr. Montaner was reunited with his family in Miami and he studied at the University of Miami. He taught American literature at the Interamerican University of Puerto Rico from 1966 to 1970, publishing his first books, including a collection of short stories “Póker de Brujas y Otros Cuentos” (“Witch Poker and Other Stories”) in 1968. He also wrote a column distributed to newspapers across Latin America.

Mr. Montaner moved to Madrid in 1970 and founded a publishing house, Editorial Playor, in 1972. In the 1980s, he began writing for U.S. newspapers, including the Miami Herald. He was editor of El Nuevo Herald’s opinion page between 1987 and 1989.

In 2013, he joined the University of Miami’s Institute for Cuban and Cuban-American Studies as a senior research associate.

Survivors include his wife Linda Montaner; two children, and two granddaughters.

In 2014, an interviewer in Cuba asked Mr. Montaner by phone if he would like to return to Cuba.

“Yes, I would,” he said. “I am nothing other than Cuban.”

“Do you think that will be possible?” the interviewer asked about a visit to Havana.

“No,” he said. “I think I will die without returning to Cuba.”