Yes, but how many are of voting age, though, and how many of those are eligible? 340 million includes everyone, including those who can’t.
The worst case estimate has it at 11 million people are fascists in the US. This is from 2018, but it gives a good ball park number for today. edit: 2018 not 2016
https://www.vox.com/2018/8/10/17670992/study-white-americans-alt-right-racism-white-nationalists