Final answer:
American styles were incorporated into ska due to the U.S. musical history rooted in African and European traditions, combined with the global influence of American culture after World War II.
Step-by-step explanation:
The reason that American styles were incorporated into ska music is grounded in the rich tapestry of U.S. musical history, which was significantly influenced by the blending of African and European musical traditions.
Early American music, like that of Stephen Foster, emerged from this cultural mix and became internationally famous. Moreover, the global influence of the United States post-World War II, through servicemen, products, and media, helped spread American music and culture worldwide.
American rock 'n' roll, with its roots in African American rhythm and blues and church music, further blurred racial lines and reshaped social interactions. It was not only popular within the U.S. but also influential on a global scale, affecting other musical genres such as ska.