It's a message that pertains from everything to the panem et circenses of Imperial Rome (as represented by Nero the Hero - in fact, all of the racers explicitly represent a culture where people were kept distracted by violence-as-entertainment) to the Panem of The Hunger Games, and it is applied to the America in which Bartel and screenwriters Robert Thom and Charles B. Griffith (largely reworking a short story by Ib Melchior) were all living with particularly entertaining didacticism; its satire is as much funny as it is probing, and thus goes down far easier than it might seem on paper.
Cinematic science-fictions variations on these themes have included "Rollerball" (1975), "Death Race 2000" (1975), "Logan's Run" (1976), "The Running Man" (1987), "The Condemned" (2007), "Series 7: The Contenders" (2001, a movie that increasingly seems ahead of its time) and Japan's "Battle Royale" (2000), also about teenagers selected to fight each other to the death in a televised reality show for the alleged benefit of society as a whole.
The gimmick of widespread murder as televised entertainment proscribed by the government to sate and distract the increasingly jaded masses would later turn up in films such as the classic 1975 Roger Corman production "Death Race 2000" and the 1987 Stephen King adaptation "The Running Man" (which, in a brilliant stroke of casting, deployed none other than game show staple Richard Dawson, in the role of his career, as the malevolent emcee).
Unless you've seen Battle Royale, Series 7: The Contenders, The Most Dangerous Game, The Condemned, Death Race 2000, Gamer, Hard Target, Surviving the Game and The Running Man, obviously.