The American mod was very real, but he was a vastly different creature from those that spawned him. In 1965 and '66, after The Beatles and other Merseybeat bands had already kick-started the British Invasion, the word "mod" penetrated youth consciousness in America via teenybopper magazines such as Tiger Beat, Hullabaloo and the perfectly titled Teen. They used the curious word when referring to the British Invasion's second wind: The Who, The Kinks, The Yardbirds, Small Faces, The Pretty Things, as well as a host of lesser-known bands, including The Creation, The Idle Race and the underrated Easybeats (who hailed from Australia, actually). Once in a while writers even pinned it to the Stones.
Most of these groups contained mods, yes. But they were mods in the process of shedding a subculture that was, in the United Kingdom, very nearly dead by 1965 and '66. The original mods rambunctious teens addicted to Vespas, American rhythm and blues, and amphetamines flourished in the late 1950s and the early part of the following decade. But they wandered from the herd after college started feeding them a steady diet of folk rock, marijuana and other mind-altering awesomeness.
You can hear these radical transformations in the music during the years in question. The Who, growing tired of playing blues and R&B classics like "I'm a Man" and "Please, Please, Please," were now writing their own tunes, dabbling in fuzzy sonic experimentation and laying the groundwork for hard rock in the process. The same can be said of The Pretty Things and Small Faces. Meanwhile, far-out acts like Pink Floyd, Soft Machine and The Move were going even further out, deep into the psychedelic cosmos. There were holdouts, namely freakbeat acts like The Downliners Sect and The Sheffields, but they were becoming rarer and rarer.
You could say the American mod was a product of an American teenybopper press short on quality cultural anthropologists capable of keeping up with the kids over in the U.K. He or she was really nothing more than a teenage Anglophile who preferred the British Invasion's loudest, hardest and weirdest bands The Beatles were just too tame.