I think you are trying to do too much.
Winning the ‘hearts and minds of America’ is a different thing from denying ‘bigots their base in the first place so it dies on the vine.’
The one you can perhaps manage in the sense that you may be able to get to a point where most Americans agree that racists and bigots are idiots whose views are not worth listening to.
Getting bigots not to listen to other bigots is a step beyond and I don’t think it is possible.
Ironically, most people thinking that the neo-Nazis are idiots is probably what got America in the state it’s in.
‘If they’re just idiotic losers then the people turning up to protest them must be even bigger idiots.’
It doesn’t help that the most vocal anti-Nazis are not surprisingly anti-fa. Anti-fa is particularly at a disadvantage in terms of mainstream opinion because they are tarred with the ‘left-wing extremist’ brush.
The US right wing has been particularly good at painting all political debate in terms of where you stand in relation to them.
If you agree with them, you are sensible and moderate.
If you don’t, you are by definition a ‘liberal’. Which means un-American, unrealistic, and worse - probably a communist.
There is no room in their narrative for a political middle ground.
By allowing that idea to take hold, any opposition to anything they espouse becomes an attack on America, on mom’s apple pie - even on baseball!
The fact that this paints them into a corner where they support Nazis because people they think of as scary, dangerous left-winger nutters oppose them is an inevitable consequence.
In addition you have the problem that most people like to think of themselves as pretty good people all in all and that their neighbours are pretty ok all in all.
Any discussion of US fascism and racism (like any discussion of racism anywhere) has to involve some very unpleasant discussions of the many ways we all feed into the institutional racism of our societies.
Basically if you publicly oppose Nazis other than by ignoring them and denying that they exist or have meaningful influence, you force Americans to consider their attitudes and require them to accept that society is fucked up in many ways and that lots of the things they do and consider beneficial are in fact harmful to lots of other people. See confederate flags, statues, standing for the National Anthem, etc.
It’s a lot easier for people to accept the narrative that they don’t need to start thinking that maybe they’ve been behaving like assholes for the last several hundred years and that instead it’s the people making them think that are the problem.
So having laid all that screed out, do I have any suggestions. Not really 
I think there is merit in pushing against the everyone who isn’t either a Republican or even further right is a communist hippy traitor narrative.
But can that be done - especially without severing ties and cutting off support from/to the actual left wingers and anti-fa? Doing that just plays in to the Nazis’ hands.
One thing that can be done but won’t be quick is to show that just because you are left wing doesn’t mean you’re a rabid communist who wants to abolish all private property and set up gulags in which nice people from Idaho will be interned.
The DSA seem to be doing a fairly good job of that with local outreach activities and so on.
