Choose the best answer. Why is the Vietnam War often viewed as a failure of American foreign policy?

When American forces withdrew, the South Vietnamese were quickly defeated, and the U. S. failed to come to the aid of their ally.

When American forces withdrew, the North Vietnamese were quickly defeated, and the U. S. failed to come to the aid of their ally.

When American forces withdrew, the South Vietnamese were quickly defeated, and the U. S. came to the aid of their ally.

When American forces withdrew, the North Vietnamese were quickly defeated, and the U. S. came to the aid of their ally.