By the same token, the U.S. seems never to have been able to plant "sleepers" in any Communist country, nor even to have recruited any spies of note. Most of our best human intelligence sources were high-ranking Communist officials who "walked in". It says much about the CIA that a number of these were initially rebuffed, and had to approach the agency several times before their services were accepted.
In contrast, most of the agents actually recruited by case officers were low ranking and of limited use. A surprising number turned out to be doubler agents--in fact, the Cuban DGI regularly made the CIA look like fools by insinuating double agents into Agency networks and expats into the Agency itself.