Was the presidency of John F. Kennedy a revolutionary period within America's history?
For the most part, it was not. The only claim that this period has to being revolutionary is the fact that much of the Civil Rights Movement occurred during Kennedy's time in office.
In terms of its politics and its economics, this was not a revolutionary time. Kennedy was not notably liberal in either of these areas. He did not do things along the lines of what Franklin Roosevelt or Lyndon Johnson did.
In terms of "mainstream" America, this was not a revolutionary time either. The Vietnam War had not really gotten started yet (not in any really big way) and neither had the counterculture. However, there was massive change going on in terms of race relations. Within this context, the presence of things like the Freedom Riders and the March on Washington would qualify Kennedy's presidency as a revolutionary time for race relations.