The opinions of peers and social media seems to power most of the clichéd responses, from what I see. It is less clear where those clichés originate or who are the originating amplifiers/influencers.
I hear people regurgitate canned memes, but it isn't obvious where they were programmed. My mum repeats some memes that I think she learnt from her peer group, even though the memes are conflicting with the underlying beliefs I know her to have.
I think you are implying traditional media and advertising has an outsized influence. That is weird to me, although I agree their influence definitely exists as a background swamp.
Edit: Is using the word “tropes” like this common? (“tropes” as used in this thread). Meme or stereotype or cliché seem better word fits for some of the usages I have read so far. I’m guessing “meme” has been stolen for visual gags.