Whenever we learn about the Cold War, we always hear about the all the times when Americans destabilized a country by becoming involved with it's politic, like Guatemala, Iran (though that came later), Vietnam, Cuba. I was wondering if there was maybe an example of the opposite, where American involvement ended up benefiting it (excluding the Peace Corps). Not trying to justify the coups, I am legitimately curious.
Well, it's a question that depends heavily on your definitions of terms such as involvement, destabilize and even Cold War. Also, it's a very politically loaded discussion, so even though I'll of course try to stay as neutral as possible, I should probably open by saying I'm pretty generally 'anti-american' and definitely pretty far to the left - at least in American terms!
In any case, my answer is yes.
I'd argue that much of Europe was in fact stabilized by American involvement in the earliest stages of the Cold War. Without strong Allied support - both political and military - to certain groups, civil wars wouldn't have been unlikely in several countries. The resistance movements were often the only 'armed force' of a country after liberation/german surrender. In Greece it became a civil war between the left and right leaning groups, almost before the occupation was over. A similar situation could easily have played out in Italy, France, etc.
I imagine the same is true for the territories occupied by Japan, but I don't know enough to make a solid statement.
Aside from this, I'd like to mention that the American involvement in Cuba could actually be seen as a stabilizing factor. Batista would never have left his position, even if he knew he had no support from across the gulf, and I think he'd still fought Castro, Che and their movement as long as he did. However, one could argue that subsequent events - such as the blockade and Bay of Pigs - played a massive part in forging a united Cuba, from what had previously been a massively varied group, only united in their opposition to the Batista regime.
I hope someone can chime in with more details about my examples or entirely new ones. While I, as mentioned, is critical of the United States foreign policy, I'm sure that there is lots of examples of US involvement being beneficial to a country that I simply don't know (enough) about. Maybe the UN peacekeeping missions, such as UNIFIL in Lebanon or on Cyprus?
A note (not really an answer): your question is a good example of something. By narrowing the scope to specifically exclude the Peace Corps, you reduce the possible answers. This practice of asking narrow questions was abandoned by the US military back in the 80s. Here's a ridiculous overblown example:
The Peace Corps specifically is one of the US's best foreign policy ideas--and it is still largely untried if you look at funding levels. The classic statement about that program is that it gets the funding of about 2 F16s. The talent sent is really no longer appropriate to the needs of most host countries. Young, inexperienced college grads do accomplish good will but little else. It would be very interesting to apply some of the discipline, mission planning and technical training from the military to this program without arming it. People not carrying weapons arriving to do good things... surprise! They do good things.