The main change that took place during these three presidencies was that the United States turned from its Cold War focus on the Soviet Union to a less coherent foreign policy that had to try to react to various events without necessarily having a strong guiding purpose.
During the Cold War, there was a clear purpose to American foreign policy. The goal of American policy during this time was to prevent the spread of communism. Everything that happened in the world could be looked at through this lens. If something threatened to allow communism to expand or become more powerful, it needed to be opposed. Otherwise, it was not of much significance.
During the three presidencies you mention, this all changed. Now, the US had to react to events in a more ad hoc way. There could be an invasion of Panama to capture their leader, later convicted of having been a drug trafficker) and try to improve the country’s human rights situation. There could be intervention in the Balkans to try to prevent bloodshed there. By contrast, there was no intervention to prevent genocide in Rwanda. It was not completely clear as to what America’s guiding purpose was.
Thus, the major change during this time was a change from a clear focus for American foreign policy to a much less purposeful foreign policy. This changed to some degree after the 9/11 attacks, but the general trend still applies.