Really? Because I can quite easily. It doesn't have to be full on Nazi Germany, but countries slide into authoritarianism all the time, the U.S. isn't special. Its institutions are rotten, its political leadership sclerotic, its elites indifferent to anything but their own comfort. I don't think it will take a particularly hard shove to topple the edifice of it as a functional, pluralistic democracy.
I think civil war is likely if it ever goes that way. And I think civil war is the only way it goes authoritarian. Classic temporary emergency powers to "protect" the republic.
I can see the US becoming an illegitimate democracy, where the institutions break down. Trump almost did it. Then comes the civil war and sweeping emergency powers. This is why I say destroying the SCOTUS by stacking the court is a terrible idea, it's one step closer to authoritarianism and civil war. It's one of the dumbest ideas I've ever heard, and could lead to civil war. The right wing fringe stormed the Capitol the last time they thought they got screwed over by the Democrats, and that wasn't even true.
But MH is right that the US also has a strong anti-government liberalism bent.