How did america’s involvement in world war ii trigger a mass migration

People moved from one place to seek work in other places.

Explanation:

During World War II, America saw many migrations within states as it encourages people to work in industries to produce war goods. Work was generally in areas with factories already built, and in larger cities. All this led to people moving to the cities to help with the war effort. Mass migration was an event that began during war when soldiers and their families assigned to new duty stations or as war workers in shipyards and aircraft factories.                            

some american cities felt workers were being oppressed by business monopolies