IMO, Senator McCain is exaggerating. It is a big leap from asserting that U.S. military intervention should be focused where critical interests exist and outright isolationism. To suggest that the U.S. military should focus its interventions in areas where critical interests or allies are threatened is not isolationism. To imply that military intervention is not necessarily the most effective or efficient approach for facilitating political change is not isolationism. To reaffirm that the Constitution is the source of authority for all American policy, including military decision making, is not isolationism.
Furthermore, Senator McCain's remarks on President Reagan are highly revisionist. President Reagan did not use military force to try to bring about political change in the Soviet Union. He used pressure from leveraging U.S. economic strength, offering a clear political message, pursuing an aggressive strengthening of American military capabilities, assisting friendly forces fighting communist insurgencies/dictatorships, and leaving an opening for conciliation. His was not a rigid "take it-or-leave it" approach. His was not an undisciplined approach that wasted American military power in areas that were of peripheral or lesser interest to the United States.