America First is explicitly a Nazi slogan, and has been for 70 years. Using "socialist" as a slur has been the rhetoric of the KKK and other racists in the United States for at last that long, designed to gin up violence against Black people, Latinos and Jews.

And definitely don't just take my word for this. there is a well documented, easily found history detailing why and how this language ha been used by the most odious elements of society to butcher non-whites.

All of which Marjorie Taylor Greene, Kevin McCarthy, Mitch McConnell and the rest of them are fully aware of. They use it/nurture it's growth in the GOP because there's a proven history of it working.