John .F. Kennedy has been one of the most successful presidents of the United States. He was assassinated on 22nd November 1963. Even after 50 years of his assassination, there is a sense of grief for having lost a capable leader who had all the potential to change the future of not just the country but also the world.
One event that would surely have not occurred is the blunder United States made in Vietnam War. Lyndon Johnson made a mistake of increasing the number of ground troops in Vietnam to fight the Chinese.  As a result, there was a huge loss of men and money. Kennedy would have considered the option of quitting the war in order to save resources. A day before travelling to Dallas, where was assassinated, he had written a note to his officials asking them to carry out an in depth analysis of every option in the war in Vietnam including the option of getting out of the war. It is noteworthy that he refrained from nuclear escalation in the Cuban Missile Crisis. So, he would not have delved deep into Vietnam War. In fact, Johnson would have never been the president as Kennedy was almost sure to win the next presidential election as well. That would have given him a chance probably to carry out his plans boldly unlike many of his successors who played it safe to get re-elected for the second term. Having said this, there would have been some negative effect as well. Johnson brought in various reforms like the Civil Rights Act and ‘War on Poverty’. One main reason why those programs were successful was that Congress was forced to implement them as they were Kennedy’s agenda and passing them was like paying their tribute to the martyr.  Had Kennedy been alive, it would have taken him considerable time if at all he was successful in passing them.
Every small event has a potential to change the sequence of events in the world for years to come. When a small event can trigger a significant change, an event as big as this was definitely the turning point in the history of United States. The history would have been quite different had this event not taken place. This was the event which brought about various changes in the mindset of people. Trust began vanishing among the people. Previously Presidents were easily approachable. This incident made them far from the sight of a common man. The politics has been considerably changed. Had Kennedy been the President, Lyndon would have never got chance. This also means that the Presidential baton would have not changed from Democratic Party to Republican Party. There may not have been any scam which further lowered the faith of people.
So, definitely this even was one its kind which had a great impact on the politics of United States.
1.Karnow, Stanley (1990). In Our Image: America's Empire in the Philippines. Ballantine books. ISBN 0345328167.
2.Gittinger, Ted and Fisher, Allen, LBJ Champions the Civil Rights Act of 1964, Part 2, Prologue Magazine, The National Archives, Summer 2004, Vol. 36, No. 2