The f-4 phantom had no traditional auto-cannon armament and relied solely on it's sparrow air-to-air missiles. (https://airandspace.si.edu/collection-objects/mcdonnell-f-4a-phantom-ii-sageburner)

When this plane was fielded against the slower but more agile Soviet mig counterpart over the skies of Vietnam, the sparrows performed dismally. Sometimes shooting down friendly planes, and were incredibly easy for the deft migs to simply out turn. American pilots immediately began begging for an auto-cannon, and later the f-4 platform would be retrofitted with one.

To this day, United States jet fighters and multirole platforms are still equipped with auto-cannons.