AP Photo

When Alberto Salazar crossed the finish line to win his third straight New York City Marathon 27 years ago, he did not think about who was coming behind him.

He just assumed that runners from the United States would always be there — until the sound of their footsteps grew fainter and fainter year after year.

With frustration, Salazar watched United States distance running become more complacent than competitive, as African and European runners captured big city marathons and American men and women seemed to concede those victories. The American men and women struggled so much...