Emotions aren’t entirely rational with a clearly thought our process to justify why one should feel them. In any case, its common enough for people to assign the general actions of people within a group to the group as a whole (which isnt really fair or a reflection of reality, but can be pragmatic at times and requires less thought and information than judging on an individual basis, so it makes sense that people’s brains are wired up to do it even if its not always desirable). This can get extended to the groups one is a part of oneself, to include those whose membership one did not choose. And the US at the moment has even worse than typical leadership, has a great deal of power for that leadership to abuse, still has free enough media for people within it to stand a good chance of knowing about at least some of it, and if youre here on lemmy youre probably running into people with a somewhat higher than normal awareness of a lot of the historical abuses previous Americans have perpetrated just because it leans left and anti-establishment and those things get talked about a lot in such spaces.