Most Americans, having not lived under authoritarian regimes or dictatorships, don't actually know what they're like. They imagine doors getting kicked in, social chaos, constant warring gangs or warlords, that kind of thing. But the truth is that society basically functions the same way it does everywhere else. People go to work, they go to the movies, they meet up at restaurants and go to religious services and form clubs. Very few people just disappear.
But everyone knows that people do disappear, and that if they're not careful, it could be them, and they act accordingly.
Americans mostly haven't internalized that yet because they think it can't be them. Oh, those people being sent to foreign prisons were foreigners/criminals/radicals/communists/antisemites/American-haters/whatever, there must have been some reason. This is America and we love freedom, the government wouldn't just scoop someone off the street and bundle them out of the country for no reason. There must be a reason. If there's no reason that would mean that it could happen to me, and for my own psychological safety I cannot consider that I am subject to having my life ruined in an instant due to things I have no power to affect, so there must have been a reason.
"What happened here was the gradual habituation of the people, little by little, to being governed by surprise; to receiving decisions deliberated in secret; to believing that the situation was so complicated that the government had to act on information which the people could not understand, or so dangerous that, even if the people could not understand it, it could not be released because of national security. And their sense of identification with Hitler, their trust in him, made it easier to widen this gap and reassured those who would otherwise have worried about it.[...]I wrote after the 2016 that we were in the final days of the Republic, it would just take some time for the country to die. Maybe we'll find a miracle cure, but I suspect not.
"To live in this process is absolutely not to be able to notice it—please try to believe me—unless one has a much greater degree of political awareness, acuity, than most of us had ever had occasion to develop. Each step was so small, so inconsequential, so well explained or, on occasion, ‘regretted,’ that, unless one were detached from the whole process from the beginning, unless one understood what the whole thing was in principle, what all these ‘little measures’ that no ‘patriotic German’ could resent must some day lead to, one no more saw it developing from day to day than a farmer in his field sees the corn growing. One day it is over his head.[...]
"But the one great shocking occasion, when tens or hundreds or thousands will join with you, never comes. That’s the difficulty. If the last and worst act of the whole regime had come immediately after the first and smallest, thousands, yes, millions would have been sufficiently shocked—if, let us say, the gassing of the Jews in ’43 had come immediately after the ‘German Firm’ stickers on the windows of non-Jewish shops in ’33. But of course this isn’t the way it happens. In between come all the hundreds of little steps, some of them imperceptible, each of them preparing you not to be shocked by the next. Step C is not so much worse than Step B, and, if you did not make a stand at Step B, why should you at Step C? And so on to Step D."
-Milton Mayer, They Thought They Were Free: The Germans, 1933-45
Appropriate ("appropriate") that this all happened on Pesaḥ, the holiday where as part of the Seder we repeatedly say "Once we were slaves, but now we are free."