It’s not that it doesn’t matter to Americans. It is worse; half the population (or at least, half the voting population), is thrilled with the development of fascism. The other half has been ringing the alarm bells for well over a decade; it seems to make no difference.
And you’re right, most Americans do not understand the privileges they have or give one single shit about democracy; it is just not a salient political issue. But eggs… don’t get me started on eggs.
It's probably a bit more nuanced than "half this, half that"; when you look at the facts, most voters aren't that extremist. A lot of votes vote one way or the other because they would simply never vote for the other.
This is why the swing voters / swing states are so important in the US, because only a few million are flexible enough to switch sides.
Of course the core issue is that there's a two party system; while I'm sure that in a healthy democracy the current republican and democrat parties would be the bigger ones, they wouldn't have a majority.
> The other half has been ringing the alarm bells for well over a decade; it seems to make no difference.
I feel like the issue there is that alarm bells in of themselves solve nothing. I won't extend that argument to one of its obvious conclusions, but instead I will say that efforts to attack education and critical thinking skills all contribute to people being susceptible to their democracy being corrupted and robbed blind - so having an educated populace with a sense of integrity and respect of human rights would help!