I don't think they do, really. Teaching of history has gotten so bad that I'll bet if you went to the beach one day and did one of those videos where you ask random strangers about WWI & WWII, most of the middle-aged & younger could tell you very little about the WWs. Hey, plenty of people don't even know what "country" we fought in the Civil War.
That surprises me though, your story. I'm very sorry you went through that. I grew up in central FL in the 60s-70s and I never saw anything like that. I suppose one would have expected it in the 40s & maybe the 50s but it doesn't seem to have been a thing where I lived. There are a large number of people of German ancestry in the USA (including some German ancestry in myself), many of whom have lived here for many generations.
The fashion now seems to be to call anyone with whom one disagrees a "NAZI". (By "Nazi", they do not mean "German national" at all—not even in the slightest. They mean "someone I hate and to whom I have attributed the greatest evils I can imagine".) They are not talking about Germans at all. They are (not to put too fine a point on it) talking about political conservatives. They are talking about me; not because of my degree of German ancestry, but because they truly believe that I and others like me are evil, racist, etc (insert perjorative-of-choice here).
They're not talking about you (or not because you're German, at least—not this time). Trust me on this, They are definitely talking about me and others like me (which may or may not include you.)
Most of those accusations are being made by people who know little of what historical Nazis even believed or stood for & thus being themselves in some significant danger of becoming the very thing they profess to hate.