The United States cannot rely on dangling a few trade goodies to get Fidel Castro to think twice about his African escapades. The United States would have to take extraordinarily tough measures against Cuba and the Soviets before the Cubans would leave that continent.

The Cuban involvement is the tonic Castro feels he must administer to prevent ideological fatigue at home.

It is ideology and a little nudge from the Soviet Union that dispatched some 50,000 Cubans - military, doctors, teachers and technicians - to combat areas in Angola and Ethiopia, to fan out into Zaire and Eritrea.

The line in Cuba, an official told me, is that the revolutionary socialist forces in the world "helped us when we needed it in our struggle against reactionary, imperialist enemies like the United States, and now it is our turn to help."

"It might appear that Ethiopia is quite distant," Castro told cheering multitudes in Havana recently, "but there are no longer any distances in today's world." Even more recently, Castro proclaimed that Ethiopian communist ruler Mengistu Haile Mariam "is the basic link between the Cuban revolution and the Ethiopian revolution," adding that Mengistu "is a staunch advocate of Marxism-Leninism."

It seems that President Carter is waking up to the increasing Cuban presence in Africa, though we haven't heard much from Andrew Young yet. In the end, there will be far more fussing about it in the United States than in Cuba, because in Cuba the "news" is disseminated long after the fact.

The official organ of the Cuban Communist Party, Gramma, devotes acres of newsprint and photos after Fidel has proclaimed the triumph. "We didn't publish articles telling any difficulties in Angola," explain* ed Elio Constantin, Gramma's deputy editor. "We didn't publish casualty figures, either.

"We are in agreement with the revolutions in Africa, but we are not as responsible as we are painted for everything going on in Africa, we are not stepping up activities around Rhodesia."

The "truth" Constantin frequently speaks of presumably includes the horror stories found in a new official book on the Ethiopian revolution. One of its revelations claims Emperor Haile Selassie had two young black Muslim girls dressed in white brought to his palace on his birthdays where they were sacrificed and their blood cast into the palace lake. Then, the article went on, "the emperor bathed naked in that water and drank of it," to prevent him from becoming "old and frail."

Whether this tale is believed by many Cubans is anybody's guess. But Cubans turn out enthusiastically when Castro gives public speeches on Africa. Afterward, according to a priest, there is talk in the neighborhoods about how difficult it is for Cubans in Africa. "Some people are not so pleased," he said. "But they accept it. Others are enthusiastic and even want to go. Nobody really opposes it."

In the United States, there is occasional chatter that the U.S. can get Cuban out of Africa by lifting the trade embargo. Cuban officials are the first to recognize that as nonsense. "Africa to us," said Wilfredo Cordoba, a top official in the ministry of higher education, "is solidarity with the international revolution. It is becoming part of the political training of our young people who go there."

There is an entire generationof Cuban youth born after the revolution of 1959 who are already described as occasionally unappreciative of the new order and take its benefits for granted. Therefore, they need a mission.

The fact that the mission fits the purposes of the Soviet Union is considered an irrational argument by a demented Yankee visitor.

When you press Cuban communist officials about fighting between other comrade states, Vitenam and Cambodia or Ethiopia and Eritrea (once saluted by Cuba as a revolutionary force), they only say it is regrettable and that they want to play a mediator's role.

They do not admit that Cubans have assisted Ethiopia against Eritrea or that there has been a blood bath in Cambodia. "We don't publish articles about the Cambodian reports," says editor Constantin. "We publish the truth and only the truth. We might make a mistake, but we never tell a lie."

The "truth" is always told by Castro, who sees himself as the charismatic leader of the Third World - which, in some ways, he is. Just as he cast out the imperialistic devils from Cuba nearly 20 years ago - so the big story goes - he will play a major role in casting out imperialistic devils everywhere (except in Latin American, where he failed).

Lately, Jimmy Carter has lamented the Cuban adventure. Still, the Cubans weren't saying bad things about him last week, and Castro even complimented him several months ago. Nixon is the president the Cubans really hate, and Kennedy follows closely.

Today the United States does little to stop the Cubans in Africa, and it is doubtful that we will. For some reason, we only talk of trade missions and widening relations.

This approach led Henry Kissinger to remark recently: "If we are forever blackmailed by the Cubans - a country of 9 million off our shores - no constructive [African] policy is possible. What has become of our country when we explain foreign policy by the myth of the invincible Cubans?"