They might not get anywhere in national elections - but with a proportional system they might get seats in state or local legislatures.
Not necessarily because they ar well liked though.
But in proportional systems there are for example protest votes when some people decide they want to "punish" the established parties by voting for an outsider party.
In Germany we had this with the right wing DVU winning around 20% in state elections some years back, or more recently the let wing Pirate Party winning seats in the Berlin elections.
Now the US of course has a bigger part of the population that is non-white - so a Nazi Party would probably have no chance just because of demographics - unless maybe in some pre-dominantly white regions.
But there are other outsider parties that might get votes - just look at the Greens for example which probably seem like the reincarnation of the Sovjet communists for many conservative Americans (and some maybe even are)

They certainly could win local or state seats as a fringe party (compared to the two big parties)