Simple question with a simple answer: The 1950s Comics Code Authority
said, comics sales per capita in every other continent (Europe, Asia, South America, Africa) are far higher, with the much-vaunted comics utopia of Japan actually just being somewhat above average compared to anywhere but burgerstan. Even American non-capeshit, like Disney's Mickey Mouse comics, are actually more prosperous outside the USA than within it where they are completely unknown.
Pre-Code, American comics were a massive industry, spanning every imaginable genre, format, and demographic audience, this was the "Golden Age"
Then Frederick Wertham, aided by the Red Scare, published "Corruption of the Innocent" as part of a moral panic crusade aimed at destroying the comic industry. Of course, this ended up succeeding in part because of willing support from inside parts of the comics industry itself, such as DC's capeshit and the newspapers' syndicated funny strips.
Having killed off everything other than capeshit & newspaper strips, this launched the "Silver Age"
of bland, unambitious, safe, marketable, comics. This worked for maybe a generation, from the 1950s into the 1960s, until the burgerstani comic industry's audience of small children and disinterested newspaper readers outgrew any serious interest in the skeletal remnants of the medium that had been allowed to survive under the CCA.
Hence, during the 1970s, readership imploded, and the rotten industry collapsed. In a fit of desperation, the CCA was dismantled. Hamfisted attempts to shove "important" messages were made to sell capeshit as socially relevant, comics turned inward, trying to establish themselves as a niche medium for geeks with soap opera-esque crossover continuity gimmicks, or appealing as a collectible "investment" vehicle off nostalgia bait like baseball cards were doing at the time. But none of it worked, it was far too late to save anything of worth, decades of the capeshit monoculture had completely sterilized the medium of any mass appeal or creative authenticity. This was the total death of American comics as a popular medium, the "Bronze Age"
By the late '80s, comics had for 99% of Americans shrunken to a cultural artifact, a curiosity of 1950s retro nostalgia, supported entirely by merchandising and licensing, with the actual comics having circulation numbers too small to actually matter as an industry. Sure, a small number of non-capeshit imprints like Vertigo and Black Horse exist, but they are trying to rebuild a cultural legacy that was completely exterminated.
A good comparison to what happened with comics, is what very nearly happened to vidya in 2007-2014, a campaign by self-promotional grifters to buy clout by leading a moral panic to destroy an entire medium.