It is very hard to write a good introduction unless we know what the rest of your paragraph (or longer assignment) is going to say. An introduction should tell the reader what is going to be said in the rest of the paper. I will guess as to what you might say in the rest of this paragraph and write an introduction accordingly.
If I were writing this paragraph, my introduction would say something like “The 1960s were a time of political and social upheaval in the United States. There were presidents as different as John F. Kennedy and Richard Nixon and there were major social movements led by people like Martin Luther King, Jr. and Betty Friedan.”
In the rest of the assignment, I would talk about the differences between the various presidents, showing how the US moved away from liberalism and towards conservatism. I would then talk about the various social movements like the Women’s Liberation movement and the Civil Rights Movement. The introduction above would allow me to write about these things in the rest of my paragraph.