The extreme aversion to socialism in a large portion of the America electorate is due to many factors, many of them deeply engrained cultural beliefs (many contradictory to reality) of self-reliance and the powers of the free market, but one of the most prominent outside of those is the legacy of the “Red Scare” and McCarthyism, even though communism is different to socialism.
And that is deeply ironic, given how MAGA, supposedly the “anti-Marxist, free market capitalist” side, has cosied up to dictatorships that are anything both those things.
It is also worth noting that Trump and co constantly referring to Harris as an “EXTREME MARXIST” is not because they actually believe that (they know she isn’t). It is a very intentional tactic to attempt to muddy the ideological waters and make it seem equally irrational (to ignorant, unsophisticated, or indifferent observers) to call him and MAGA fascist.
It is a very common tactic by fascists. And, although it is incredibly transparent to students of history, it unfortunately works for his fan base. And those backing him that are educated and sophisticated enough to know that is what he is doing (and why) are perfectly happy to parrot it for their own aims (primarily, and again ironically, to partake in the free for all of government money and favours that would flow to sycophants after Trump regains power).
It’s also worth nothing that many Americans don’t even know what socialism is, largely due to poor education (or miseducation). Many of them are the first to scream and shout about progressive policies that are “socialism run amok and will destroy America”, whilst in the very same breath threatening to rise up en mass and hang anyone trying to cut Social Security, Medicare, or Medicaid.