A lot of people answering here don't even seem to know what a 2nd world country is. To be clear, the phrase "second world" did no exist as a means of classifying countries before the Cold War. First World: US and its allies (NATO, Japan, S. Korea, etc). Second World: USSR and its allies (Warsaw Pact, etc). Third World: Literally everyone else. This is a military distinction, not an economic one.

As far as your question goes, probably not. It seems that the closest we ever came was in considering stabilizing Iran in the 1950's instead of overthrowing Mossadeq. Iran had just kicked out the British, and was beginning to lean toward Russia and away from the US and its allies. There were talks of giving them a large sum of money to stabilize the government, but it never happened. Mossadeq thought that playing hard to get would make the US and allies offer more support, but the opposite occurred, and the Iranian government was overthrown by the West.

If the US ever did stabilize a 2nd world country it would not be made publicly known. The political repercussions would have been insane. The implication behind your question is, "Did the US ever strengthen a Soviet Ally/US enemy?" Putting it in those terms illustrates how counterproductive such an action would have been. It is an interesting question, but really probably not.

For more info on the history of the CIA I would check out my reference, "Legacy of Ashes" by Tim Weiner.

Edit: spelling