Here's the problem as I see it (not necessarily constrained by POD mentioned in OP).
*Latin America had a pretty strong
aprista tradition which sought to adapt Marxism to Latin American conditions, ending up as the Latin American counterpart to Western European social-democratic parties. This was in the face of Orthodox Marxists who believed, much like with Russia, that Marxism (and thus the communist utopia) could never be achieved there because it was too backward (aided by the fact that Marx said very little about Latin America and what few things he did say were pretty negative, if not racist, towards Latin Americans). Thus, it follows that Marxism originally was a fringe movement largely among European immigrants, so therefore the Southern Cone became fertile ground for Marxist-inspired socialist and communist movements. Aprismo, by contrast, contradicts Orthodox Marxism by stating that the revolution can still happen in Latin America - it just needs adaptation, and in this case it involves a broad alliance including indigenous and peasant communities (early echoes of Maoism in this case, IMO). Note, here, that aprismo is not the only movement that sought to reinterpret foreign ideas to peculiar conditions -
arielismo, for example, sought to change perceptions of the Hispanic legacy in an almost Romantic mood after decades of demonizing Spain and Spanish culture, although it never developed a political base. Aprismo as a movement began to moderate and move towards social-democratic currents due to the nature of Latin American politics and the retention of an older, medieval corporatist framework - in order to gain access to the system (waiting for its "turn") it had to defang itself. If you want to change aprismo's fortunes on this score and create more populist democratic-socialist regimes (although not communist, after WWII they would be seen by Washington, gripped in McCarthyite hysteria, as "communist" but probably workable, à la Yugoslavia) you'd have to prevent the aprista parties from moderating, putting them all in the same boat as the Peruvian party in terms of oppression, only to lead to replications of the Mexican Revolution throughout Latin America where the aprista party comes out on top. (In this sense, the broad movement in Venezuela against the dictator Pérez Jiménez could be seen in this vein, although it led to a predictable alternation between the Christian democrats and the aprista Democratic Action, as would the formation of the Commonwealth of Puerto Rico and its dominance by the PPD, although like in Venezuela it just led to a regular democracy instead of a socialist state because the PPD faced little if any persecution unlike most in the Puerto Rican nationalist movement.)
Further info: The sub-section on the Apristas under the section of "The major movements"
here, as well as
Harry Kantor's seminal study on aprista ideology
*Alternatively, along similar lines, have Mariátegui's Marxist views become more widespread throughout Latin America, forming a basis for reception of Communism (cf. <
http://isj.org.uk/jose-carlos-mariategui-latin-americas-forgotten-marxist/>, <
https://isreview.org/issue/96/mariategui-and-latin-american-marxism>)
*If we limit ourselves strictly to the POD, then we have a problem in that the few exceptions of Communism in Latin America are those that prove the rule in Latin America, which is that Communism doesn't really work all that well in Latin America, and most regimes that were daubed as "Communist" by the US and the Latin American political Right were anything but Communist - most of them were boiler-plate standard democratic regimes that wanted to follow the same path the US did a couple of decades earlier (Guatemala is a case in point here). Communism in Latin America never really was a mass movement but was more a middle- to upper-middle class movement of young people, supposedly in defense of the lower classes but was anything but (the lower classes knew better and preferred to remain with the devil they knew, in general). Thus it would be very difficult, if not impossible, to flip Latin American countries during the Cold War period towards the "Reds"; that Cuba and Nicaragua managed to do so at all IOTL was basically due to strokes of good luck and could be easily reversed early on. (Likewise, Mexico is a no-no for flipping Red since the príista establishment would not allow it - the Communists were co-opted early on and served as nothing more than window-dressing for the PRI.) Leaving aside Cuba and Nicaragua, if you want to make Communism more palpable for Latin America and break out of its shell, you have to make Communism Latin American, in which case it paradoxically ceases to be Communist - at least by "normal" definitions. (If you define Communism as what developed in the USSR, there's much of it which is basically impractical except the tyrannical neo-Tsarist control that the Kremlin had over its people, which could be replicated in Latin America in manners long familiar to the population since the days of Spanish colonialism - not so much in Brazil, which marched to its own drum.) Communism would thus need to make a similar adaptation akin to what Marxism in general did pre-WWII by figuring out what could be used, and in this case the only Latin American country I can see which could be susceptible to Communism - since it was the birthplace of trying to adapt Marxism to Latin American conditions, not to mention the left-wing military dictatorship IOTL and because Communist rhetoric is more appealing to poor countries in similar situations to Tsarist Russia - is Peru. Not Cuba. Not the Southern Cone (Communist rhetoric doesn't work well in highly developed countries - not even Argentina, the most corporatist of the Latin American countries and thus saw an earlier breakdown of the system before everyone else). Not Colombia. If you want to make Communism work in Latin America, start with Peru - particularly if the Apristas are repressed to such a degree that they no longer are a viable moderate option, leading to more radical solutions becoming more appealing. If it becomes "successful", then you may have a few other poor Latin American countries go along with it. If it does not - then you have a Venezuela-like situation several decades early, with the rest of Latin America very glad to get rid of that Communist cancer and bring Peru back to normalcy.