Most Americans had a fairly negative view of Hitler, as he was hostile to America's biggest ally, Britain, and his open hostility to democracy and individual liberties was pretty negative in most Americans' eyes. Also, while America was still a very racist society in the 1930s, many saw Hitler's treatment of Jews as being unacceptable and monstrous.

I read an interesting article that compared two boxing matches between a white German boxer and a black American boxer, one in 1937, and then a re-match in late 1938. The first time, the sports media in America were broadly supportive of the German boxer, even going so far as to call him the "Great White Hope" because many racist sports fans did not want to see a black boxer become an international heavyweight champion.

But a year later, when war was clearly brewing in Europe, caused by Hitler's aggression, the narrative flipped, the American sports media cheered for their local black boxer, as a patriotic champion against foreign Nazi authoritarianism. And they also portrayed themselves (Americans) positively as anti-racists who didn't care what color skin the boxers had, as contrasted with the supposed Nazi leanings (and therefore racist leanings) of the German opponent.

Related: what was the reaction of people in the US to the Beer Hall Putsch? Was it even a widely known event in the US, at the time it happened?