While writing my senior thesis on the Ku Klux Klan, I noticed that a lot of their rhetoric was directed towards East Asian men, particularly Japanese immigrants, as not only trying to take control of the West Coast of America but also stealing white women, just like how Black men were feared to do in the South. This rhetoric was from the 1920s, so World War II was definitely not the catalyst for it. It’s a far cry from the stereotyping today of Asian men being more submissive and asexual.
While you wait, you may be interested in this reply from /u/walpurgisnox about early Hollywood portrayals of Asians and Asian Americans, through the lens of film star Sessue Hayakawa. Many modern-day stereotypes about Asian men seem to date back at least to his time and would have been recognizable to contemporary audiences.