>>One question: Why do you think the embargo is responsible for the poverty in Cuba?

Cuba calculates that the embargo cost it " 753 mil 688 millones de dólares" (over $753B, see http://www.cubavsbloqueo.cu/sites/default/files/InformeBloqueo2016ES.pdf )

It's also cost the US between $1.2B and $3.6B/year depending what you ask. There's also reputation effects: some Americans like to scoff at the UN and its annual denouncement of the embargo as illegal and against the US charter, but it has caused a great deal of reputation damage even amongst friends in Europe and Canada as well as in 3rd world and developing nations. Here's what Moisés Naím wrote in Newsweek in 2009: "The embargo is the perfect example used by anti-Americans everywhere to expose the hypocrisy of a superpower that punishes a small island while cozying to dictators elsewhere."

Cuba represents the worst sort of brinksmanship: a big boys' game of chicken that almost led to armed conflict between the US and USSR. Quoting from Wikipedia for the first few years of Castro's campaign:

The United States imposed an arms embargo on Cuba on March 14, 1958 during the armed conflict between rebels led by Fidel Castro and the Fulgencio Batista regime. The arms embargo had more of an impact on Batista than the rebels. After the Castro socialist government came to power on January 1, 1959, Castro made overtures to the United States, but was rebuffed by the Dwight D. Eisenhower administration, which by March began making plans to help overthrow him.

In May 1960, the Cuban government began to openly purchase regular armaments from the Soviet Union, citing the US arms embargo. In July 1960, the United States reduced the Cuban import quota of brown sugar to 700,000 tons, under the Sugar Act of 1948 and the Soviet Union responded by agreeing to purchase the sugar instead.

In October 1960, a key incident occurred that led to the Cuban government nationalizing all three American-owned oil refineries in the nation. Cuba nationalized the refineries following Eisenhower's decision to cancel 700,000 tons of sugar imports from Cuba to the U.S. and refused to export oil to the island, leaving it reliant on Soviet crude oil that the American companies refused to refine, which led to Cuba's nationalization response. The refinery owners were never compensated for the nationalization of their property. Today the refineries are owned & operated by the state-run company, Unión Cuba-Petróleo. This prompted the Eisenhower administration to launch the first trade embargo—a prohibition against selling all products to Cuba except food and medicine. The Cuban regime responded with nationalization of all American businesses and most American privately owned properties on the island. No compensation was given for the seizures, and a number of diplomats were expelled from Cuba.

The second wave of nationalizations prompted the Eisenhower administration, in one of its last actions, to sever all diplomatic relations with Cuba, in January 1961. The U.S. partial trade embargo with Cuba was continued, under the Trading with the Enemy Act 1917.

After the Bay of Pigs Invasion in April 1961, which had been largely planned under the Eisenhower administration, but which Kennedy had been informed of and approved during the months preceding his presidency and in his first few months as president, the Cuban government declared that it now considered itself Marxist and socialist, and aligned with the Soviet Union. On September 4, 1961, partly in response, Congress passed the Foreign Assistance Act, a Cold War Act (among many other measures) which prohibited aid to Cuba and authorized the President to impose a complete trade embargo against Cuba.

On January 21, 1962, Cuba was expelled from the Organization of American States (OAS) by a vote of 14 in favor, one (Cuba) against with six abstentions. (See Cuban relations with the Organization of American States for details of the proceedings.) Mexico and Ecuador, two abstaining members, argued that the expulsion was not authorized in the OAS Charter. (Multilateral sanctions were imposed by the OAS on July 26, 1964, which were later rescinded on July 29, 1975. Cuban relations with the Organization of American States have since improved, and as of June 3, 2009, membership suspension was lifted.)

President John F. Kennedy extended measures by Executive order, first widening the scope of the trade restrictions on February 8, 1962 (announced on February 3 and again on March 23, 1962). These measures expanded the embargo to include all imports of products containing Cuban goods, even if the final products had been made or assembled outside Cuba.

On August 3, 1962 the Foreign Assistance Act was amended to prohibit aid to any country that provides assistance to Cuba.

On September 7, 1962 President Kennedy formally expanded the Cuban embargo to include all Cuban trade, except for non-subsidized sale of food and medicines.

Following the Cuban Missile Crisis (October 1962), Kennedy imposed travel restrictions on February 8, 1963, and the Cuban Assets Control Regulations were issued on July 8, 1963, again under the Trading with the Enemy Act in response to Cubans hosting Soviet nuclear weapons. Under these restrictions, Cuban assets in the U.S. were frozen and the existing restrictions were consolidated.