"Ask not what your country do for you, rather ask what you can do for your country". These word of President John F. Kennedy inspired a generation of Americans to seek to better the lives of people in this country and of the world. It was the foundation of the Peace Corps, it helped bring young college students down to southern states to fight for desegragation. He continued "I say to fellow governments ask not what America can do for you, rather, ask what we can do together". Europe took hope that the Iron Curtain would be raised and that America intended to help people who help themselves.
It also drove many young men and women to enlist in the armed forces to spread democracy around the world. The idealism of many men and women faded as the Vietnam War broadened, and the lack of empathy among the Vietnamese people to act like Westerners.
The events of the 40 years put a damper on the spirit that drove the America of the 1960's compared to today's America. President Obama resurrected the concept as the need for change. President Kennedy offered hope to nations that a new era of leaderhsip had taken control of the U.S. when he said, "That a new generation, born in this century has stepped forward to lead the nation".
The most important effect of this speech is that the rhetoric that JFK deployed when talking about communism helped lead to the deepening US involvement in Vietnam as well as to such things as the Bay of Pigs Invasion and the Cuban Missile Crisis.
In the speech, Kennedy promised
that we shall pay any price, bear any burden, meet any hardship, support any friend, oppose any foe to assure the survival and the success of liberty.
By saying this, he was essentially writing a blank check. He was saying that we would do absolutely anything to contain communism. It is not possible to conclusively link this speech to the policies I mentioned above -- you can't say that the speech forced us into those policies. However, by publicly making this statement as one of his very first statements as president, JFK was making a very clear promise. This promise helped lead to actions (like the Vietnam War and the Bay of Pigs invasion) that, in retrospect, were unfortunate to say the least.