You’d think a hegemony with a 100-years tradition of upkeeping democracy against major non-democratic players, would have some mechanism that would prevent itself from throwing down it’s key ideology.
Is it really that the president is all that decides about the future of democracy itself? Is 53 out of 100 senate seats really enough to make country fall into authoritarian regime? Is the army really not constitutionally obliged to step in and save the day?
I’d never think that, of all places, American democracy would be the most volatile.
Normally, it would be the electoral system that would act as the check. But otherwise, it doesn’t put any other limits based on political belief and affiliation (other than having allegiances to other political powers). If the majority wanted to elect someone who wishes to abolish the democratic election system, then that is what they will get.
That’s possibly for the better. Being able to bar given political alignments or affiliation from office would either need to be so specific so as to be useless (a modern nazi typically has little directly to do with the original), or be broad enough that it’d be a dangerous thing, since it could be used in either direction.