What was a major factor leading to the erosion of regional cultural differences in the 1920s?

A major factor leading to the erosion of regional cultural differences in the 1920s was the rise of mass media, particularly radio and cinema, which facilitated the widespread dissemination of popular culture across the United States. This exposure to national trends in music, fashion, and entertainment diminished the prominence of local customs and traditions. Additionally, increased mobility through automobiles and improved transportation networks enabled people to travel more frequently, further blending regional identities. The overall atmosphere of the decade, characterized by a desire for modernity and social change, also contributed to this cultural homogenization.