This is a great quote and says a lot about how mass media has worked, historically… But what I find a little lacking is who is behind the shaping of the message in the medium. I notice that when we talk about, say, Nazi Germany or the Soviet Union, we often know who is putting out the message, the goal, and how unified it was… Which makes sense - these were clearly state-run apparatuses, which particular individuals we can point to shaping their messages. Ultimately, Goebbles was responsible for the messages put out by the Nazi mass media - even if not personally responsible. Individuals working within the system had to conform to his dictates… the Soviet Union had a state-based, more centralized body for shaping propaganda at home and abroad… probably a bit more diffuse, depending on the period, but Glavit - or the General Directorate for the protection of state secrets in the press - seems like it was the primary body for shaping the main body of propaganda. So, we can easily point to specific bodies as shaping propaganda in these more top-down situations. The state in both cases played a major role in creating propaganda and shaping public understandings both within and without these countries.
We aren’t used to thinking of the US doing something similar, because those are “oppressive” places pushing lies to justify itself. We don’t think of the US government having a propaganda arm, but we have had historically, and that arm is the American popular mass media (hollywood, the recording industry especially). Capra’s film is a perfect example of that, of course. And other people who worked in private industry also worked for the US government at various points. Stan Lee worked in propaganda during the second world war - Dr. Suess did, etc. I think people who have some engagement with World Wars and Cold War history might be familiar with this idea - that the US relied on people in private industry to shape the domestic and global perception of the US…
But what about those within these industries were went against the grain. Someone like Dalton Trumbo is an example of someone in Hollywood who used his position to promote alternative political views - he was high profile enough to get him blacklisted for a while. None the less, he keep working despite being in the Black list… Several of the films he secretly wrote won oscars for examples…
I think the reality of this shows us something interesting - that even as the US government agencies (like the CIA) seek to promote a particular set of ideas and to use mass media to do that, the mass media is not always functioning in lock-step with the government. Rather, while many people in positions of power in the mass media, it’s still a web of interconnection rather than a top-down pyramid (and probably a survey of the sources with regards to the Soviet Union or other communist countries). That doesn’t mean that the government doesn’t shape mass media to some degree, or that propaganda isn’t “real” with regards to American mass media… I just want to note that it’s not as top-down and lock-step as we often imagine it to be - because the “ruling class” in America is a bit more diverse than that, and holds a variety of political positions. I don’t think that Capra was “brainwashed” but participated because he believed in the cause. So did Trumbo, who wrote Thirty Seconds Over Tokyo, but later turned his anti-war novel Johnny Got His Gun into a film in the early 70s (at a time when anti-war sentiment was very high).