The effects of the blockade on Cuba have certainly not been the ones hoped for by the United States.
The embargo was imposed on Cuba in the early years of the Revolution. Eventually, it prohibited all trade between the two nations and even harassed foreign companies dealing with Cuba.
Since then, anti-Cuban laws have been strengthened. Most important is the recent Helms-Burton Act.
These laws were intended to worsen conditions in Cuba to the point that the Cuban people would rise up against the Cuban Government and establish a capitalist government friendly towards the United States. Effectively, this policy aims to starve Cubans into accepting capitalism.
These laws, especially the Helms-Burton Act, have been disastrous for the United States and its goals for Cuba.
In Cuba, the Cuban Government has used the U.S. action to explain the poor economic conditions. Whether or not this analysis is fair, it has been convincing enough to gain support for Fidel Castro and strengthen the government.
The U.S. position has also lessened its power in the international system. The United Nations has condemned the blockade, and many countries have objected to the extraterritoriality of the law. Support for Cuba has come from resentment towards America.