Indeed, they had opposition. However, the way we have been taught history has been laundered to make us think that Nazi ideology never had a significant base of support outside of Germany, when the truth was that it was not only significant, but segregated American society under Jim Crow was in several ways a model for the Nazis.
US treatment of migrant workers under the Bracero program and US usage of Zyklon B on migrant workers as a delousing agent directly inspired Nazis. This came to a head at the so-called bath riots in 1917: