Final answer:
The modern art movement in America started with Realism, which emerged in the early 20th century. American artists began to break away from European influences after the Armory Show in 1913, leading to the emergence of distinctively 'American' forms of painting.
Step-by-step explanation:
The modern art movement in America started with a. Realism. Until the first decade of the 20th century, American art was influenced by European styles, particularly French Impressionism. However, after the Armory Show in 1913, American art began to experiment with different styles and ideas, leading to the emergence of distinctively 'American' forms of painting. American Realism, exemplified by the Ashcan School, played a central role in this new American Modernism.