Final answer:
The emerging style of "musical Western" helped country music go from a regional genre to a national sensation in the 1930s. Option c is the answer.
Step-by-step explanation:
One impact of the emerging style of "musical Western" on the United States in the 1930s was that country music evolved from a regional genre to a national sensation. During the 1930s, the United States experienced the Great Depression and the Dust Bowl, which had significant effects on American society and culture. The popularity of Western movies and the musical Western genre played a role in the popularization of country music, elevating it beyond its regional roots in the South and West to become part of the mainstream American culture and entertainment.