I think economic collapse and/or low grade civil war and political dissolution is far more likely than full blown fascism. Unlike the Nazi leadership (especially Speer, Himmler and Goebbles), Trump is an incompetent buffoon with no real mass organization behind him. Running a true fascist state in a nation the size of the U.S. would take at least a million enforcers and an astronomical amount of money to construct the right infrastructure. Meanwhile, America is deeply in debt, vastly overextended around the globe and virtually hollowed out from within after 35 years of rampant neoliberalism.
That’s not to say that the economic and political collapse of America will be fun by any means. It will still be horrific, just in a much different way than having jackboots marching down every street.