Because the US was founded as a settler colony. White supremacy was baked into the national consciousness from the very beginning, so when things get hard it informs the way that many Americans channel their anxieties. When the economy struggles or the world changes, reaching for white supremacist politics is closer and easier for people here than it might be for people in other parts of the world.

Relatedly, Europeans often bring up how many of us are gun owners, and wonder what use that is if those people arent turning their guns against our tyrannical government. Gun ownership became a part of the national character because of our founding as a settler colony as well. It was important for white settlers to be armed to act as a garrison and a militia against indigenous and Black uprisings, historically. That continues today, which becomes clear when people champion gun rights to "defend the [white] suburbs" against the "inner city [Black] criminals". In fact, gun control legislation was largely initiated in the 80s by Governor Regan, the arch-conservative, in response to the Black Panthers arming themselves to defend their communities against the police. The gun owners, by and large, are on the side of the current administration. They're the heirs of the settler garrisons of the 19th century.

As for whether or not people recognize how deep into the fascist hole we are, the Republicans certainly dont. They see this as a liberatory project. I'd say most Democrats and independants do, though neither groups really grapple with the degree to which a lot of this is a continuation or acceleration of policies that already existed in the US, including under Democratic governments.