Donald Trump exhibits every defining factor of being a fascist. He's authoritarian and very pro-military, he's nationalistic, he paints other religions and ethnicities as being evil, he paints other nationalities as being evil, he is protectionist, he's anti-media, he's anti-independent judiciary...
> paints other religions and ethnicities as being evil
> paints other nationalities as being evil
> anti-media
> anti-independent judiciary
None of those views fall very far outside of mainstream Republican belief. Trump just replaced the typical dog-whistle with a bullhorn, because he's politically incompetent, and was far more blatant in pandering openly to the fringe.
The difference is he has a personality disorder, extreme narcissism, that verges into sociopathy. If such an individual gets hold of a position of power, they can ruthlessly "split" the people around them, and exert greater than proportional influence. Whether this meets a technical description of fascism or not, it puts him in a category with authoritarian despots, who rule with no regard for the welfare of anyone besides themselves.
None of those things (except pro-military, but every party in the US is pro-military, that's what you get when you're the only empire on earth) are typical of the republicans. The republicans, despite what you might (incorrectly) think, are not represented well by Trump.