The johnson-reed immigration act of 1924 did not affect the

Immigrants from Northern Europe particularly Great Britain and Ireland were not affected by this act because they had many cultural similarities with Americans. Also, the act it set no limits on immigration from other countries of the Americas.

geography

this is because warmer climates often don't get people sick from the flu and regions where it was often colder more people received the flu. hope this if you need more reasoning i am here to