People from all three eastern regions migrate into the midwest, great plains and the western united states. why then is there a relatively uniform form of english spoken across this enormous area

There is a relatively uniform form of english dialect spoken across this enormous area because of the mobility and migration of Americans allowed for a uniform dialect to spread across the country. Ther reason why there are relatively uniform of englsih dialect across this region (Southeastern, New England and Midlands) because of the migration and mobility of Americans allowed for a uniform dialect to spread across the country.