In our TL, the U.S.'s immigration system--which favored immigration from Northern and Western Europe--got significantly changed in 1965 when the U.S. opened its doors to immigrants from Asia and other parts of the world.
Meanwhile, my question is this--without WWII (such as if Adolf Hitler gets killed in 1923), how much longer would the U.S.'s pro-Nordic immigration system (based on the Immigration Act of 1924) remain?
Any thoughts on this?