Germany was prostrate, disarmed, and bankrupt, humiliated by the Versailles Treaty, with its industrial heartland in the Ruhr under military occupation. Hyperinflation was rampant. The capitalist system was tottering, racked by widespread industrial strife and threatened by the rapid growth of a mass communist party.
By contrast, the US is still the most powerful economic and military power in the world, notwithstanding its losses in Iraq and Afghanistan. Growth and real incomes are stagnant, but official unemployment is under 6% and concentrated outside the major urban centres. Dissatisfaction with the system has increased, but there is no threat to the system from below in any way comparable to that in Germany in the immediate aftermath of the Russian Revolution.
Trump is a narcissistic opportunist who is exploiting the ugly racism and fears of American society, but the material conditions in the US are not yet so dire as they were in Germany to provoke a mass movement from the established parties and electoral system, nor do the changing demographics of the country favour such a development.
Neither is there any incentive for US corporate leaders to throw their weight behind Trump, as there was for the German capitalists who supported Hitler, alarmed as they were at the time by the inability of the governing conservative and social democratic parties to quell the strikes and demonstrations and other manifestations of working class unrest, expressed politically in the rise of the German Communist Party (KPD).