Here is what the article says about Cuba:
Until 1992,[84] Cuba was officially an atheist state...[8][85]
Originally more tolerant of religion, the Cuban government began arresting many believers and shutting down religious schools after the Bay of Pigs invasion. Its prisons were being filled with clergy since the 1960s.[87] In 1961 The Cuban government confiscated Catholic schools, including the Jesuit school that Fidel Castro had attended. In 1965 it exiled two hundred priests.[88]
In 1976 the Constitution of Cuba added a clause stating that the "socialist state...bases its activity on, and educates the people in, the scientific materialist concept of the universe". In 1992, the Dissolution of the Soviet Union led the country to declare itself a secular state...
So, originally more tolerant of religion, Cuba began to crack down [might one add 'almost inevitably'?] on religions, until it declared itself a secular state. Similar to what happened in the Soviet Union. How is that against my hypothesis?
As for Vietnam: where did you get your information from? Here is the Human Rights Watch non-profit group:
Vietnam: Sharp Backsliding on Religious Freedom
There are lots of articles of Vietnam cracking down on religious groups, especially Buddhists and Catholics.
While of course there are political aspects to this, I suggest that it may well be inevitable for an atheist state to take on the idea that religions should be restricted and eventually eliminated, much like some atheists like yourself and Dr Dawkins believe that telling children they belong to a religion is child abuse, and then acting on that idea when given sufficient political power.