* Prohibition only covers distilled alcohol, not beer or wine. How might that impact the development of organized crime, corruption, resistance to Federal authority, disruption of portions of the economy, etc.
* Alfred Mahan's impactful book "The Influence of Seapower on History..." either doesn't get written or remains a dusty dry tome on the far back shelves in the third sub-basement of the Library of Congress. The Kaiser, etal then don't use this work to help justify the battleship building race of the early 20th Century (This might be a timeline where it's more about what doesn't happen...) A possible offshoot of this POD, is that the "Jeune Ecole" concept has more legs (or fins....)
* J. Edgar Hoover doesn't go into law enforcement. A POD? Maybe he gets drafted on completion of college 1916 and gets sent to Mexico with the Pancho Villa Expediton.
* Cable TV never becomes a dominant program distribution technology.
*edit* These are fair game for anyone to tackle as their own TL.