The Amsterdam All-Stars are a fictional New York City gang in 1979.
Formation and Background
Little is known about the Amsterdam All-Stars' formation, except that they were founded sometime before July 12, 1979. They were on the Gramercy Riffs' network.
When Cyrus and the Gramercy Riffs called a conclave of New York City's gang, nine delegates of the Amsterdam All-Stars were sent to the meeting on behalf of the gang. At the meeting in Van Cortlandt Park, the Bronx; it is unknown what became of the gang's delegates when Cyrus was shot and the meeting was interrupted by the cops.
In the Film
They attended Cyrus' big meeting.
In the Game
It's possible they were in that large cutscene at the big meeting.