The organization Friends Of New Germany was formed around this time with help of the German consul in New York. However its membership was limited between 5,000-10,000 and it was limited to Americans of German descent or naturalized German immigrants. The organization was investigated by Congress because of its fascist political stances and the German American Bund was subsequently the successor. I think this shows at least some limited popularity for Hitler, though he was particularly unpopular with many Americans.

A reminder to everyone to keep things in topic, and that answers are expected to be indepth and comprehensive. I've had to remove a single link to a Times piece and a discussion on Canadaian politicans.