Depends on your definition of "Catholic populations" (i.e. practicing Catholics versus poorly catechized members who do not adhere to the Church's teachings - IOW "Catholics in Name Only").
"While Latin-American Catholics are still more socially conservative than those in the United States and Europe, there’s still an important gap between popular religiosity and doctrinal adherence. Popular Catholicism across the region is a syncretic mix of precolonial beliefs, African-influenced religious practices, rural and popular folkways (such as shamanism and curanderismo), and personal and regional devotion to individual saints. To the persistent frustration of the Catholic hierarchy from colonial times to the present, Latin-American Catholics have had historically low rates of sacramental participation, especially among the poor. Relatively few nonelite couples, for instance, chose to participate in the sacrament of marriage. This practice goes back to the colonial period. Historically, Latin Americans have had markedly lower levels of Mass attendance than those in the United States".
http://commonwealmagazine.org/church-latin-america
It's disingenuous to attempt to implicate Catholicism as a causal factor of the growth of marxism/socialism by indicting some groups of baptized members who have either rejected or have failed to receive her teaching and thus fail to follow the "holy way".
Catholic population means a population of Catholics, especially a high portion of the Catholics in a population when talking about almost purely Catholic nations.
By the way, it would sure be better if you would just respond to own posts when posting to me rather than creating things that I haven’t said or claimed.