Earlier quoted context omitted.
What's your constructive result (as opposed to reactive/condemning) of that characterization? To me, propaganda is just a result of mass media, which itself is a result of the longer trend of advancing of communication technology. It's impossible to oppress someone who is not in your "light cone", or to control actions which are below your limit of resolving. In the past things weren't as developed, so it was easier…
Not just mass media. In Bernays' Propaganda , he describes a new process to sell pianos based on psychoanalysis rather than traditional big-print advertisements. Essentially, get leading architects to incorporate "music rooms" into their residential designs. Most architects will follow the greats and add music rooms as well. The average homeowner will then walk into the hardware store someday and notice a piano for s…
I think you have mistakenly limited "mass media" to radio, telegraphy, TV, etc., and omitted print.
As a reminder, "big-print advertisements" have been around for a long time. The penny press predates useful electric telegraphy, though just barely. https://en.wikipedia.org/wiki/Newspaper#Industrial_Revolutio... says "In France, Émile de Girardin started "La Presse" in 1836, introducing cheap, advertising-supported dailies to France." 60 years previous, Thomas Paine's "Common Sense" pamphlet was distributed by the 100,000s during the US revolution, and I would put that as part of mass media and political propaganda.
Aspect of mass media in Europe of course go all the way back to Gutenberg. I'm not trying to establish a certain date, but rather demonstrate that mass media and its effects on propaganda have been part of the US for its entire history.
Even your 1917 is a semi-arbitrary date. Why not the yellow journalism of the 1890s, or more specifically the propaganda of the Spanish–American War ?
Going back further, the 1840 campaign song "Tippecanoe and Tyler Too", coupled with printed sheet music, helped bring Harrison to power. I'm a bit iffy of if that counts as mass media, but if not, it's close. Quoting https://en.wikipedia.org/wiki/Tippecanoe_and_Tyler_Too , that song "firmly established the power of singing as a campaign device", and surely was not ignored by future candidates.