US' Reaction to Castro's Death

I read a relatively comprehensive article on this topic some times ago, and apparently there are several potential “next in line”, apparently divided into two clans. Don’t ask me anything more, I don’t remember the names/details. I just vaguely remember that one group is mainly made of the “close collaborators/family/friends of old” and the other of “young sharks”. So it seems that there could be some internal strife after Castro’s death.

El caballo muerte nunca!!

                                   (Fidel will never die)

Is Cuba the only country left in the world that is still experiencing if the socialism system is working or not?