DW Griffith never makes the film Birth of a Nation. Instead, his first film upon joining the Mutual Film Corporation is The Mother and the Law (i.e. basically the same as the "Modern Story" from his OTL film Intolerance, which he'd already been writing when he was making Birth of a Nation in OTL). This is followed by the epic The Fall of Babylon (i.e. the "Babylon Story" from Intolerance).
I'm thinking in terms of the cultural influence that Birth of a Nation had. For instance, it's blamed for inspiring the revival of the Ku Klux Klan. If the film was never made, what would happen afterwards?