Walter Kaufmann taught at Princeton University from 1947-1980. He was born in Germany and came to America in 1944. He is credited with the translation of Nietzsche’s works. See more here

Professor Kaufmann discusses Sartre, Jaspers, Heidegger, Kierkegaard
“Kierkegaard would have felt that if Sartre was an existentialist then he was not an existentialist. Link to a 60 minute interview from 1960.

Kaufmann discusses the modern crisis (1960) in Religion, Morality, and Philosophy

Kierkegaard and the Crisis in Religion Audio 1973
“The term existentialism was coined about 30 years ago by a couple of German philosophers, Karl Jaspers and Martin Heidegger.”

Nietzsche and the Crisis in Philosophy Audio 1973
“The question was, Seeing that Kierkegaard has such terrible views why should we study him. I think that question is applicable to Nietzsche.”

Sartre and the Crisis in Morality 1973 Audio
I do believe that this great development of the sciences has an enormous amount to do with what I have called the modern crisis.