> As a Russian, who was born in USSR, I regret that CIA has failed to assassinate him 50 years ago.
Your problem is thinking that covered operations make the world better. It obviously didn't work in Iran, Vietnam, Cambodia, Congo, Argentina, Venezuela, Colombia, Bolivia and many others countries. In fact it made the situation worse in most cases.
Because just topping dictator is not enough, you also have to manage coup and support right side (i.e. those who are in favour democracy, secularism and market economy).
US sucks at finding and supporting right side.
If US just assassinated Castro but did nothing else communist regime won't fall, it can even gain stronger support from masses. The coup should be well prepared and US should feel responsibility about what will happen after.
Coup is definitely very difficult and complicated surgery.