Final answer:
Auden is considered an Anglo-American poet due to his British origins and subsequent American citizenship, reflecting literary traditions from both England and the United States.
Step-by-step explanation:
W.H. Auden is considered an Anglo-American poet because of his British birth and his later American citizenship. Auden was originally a part of the British literary scene, and his early poetry, which included the technical skill and command of historical traditions of English poetry, firmly rooted him within that context.
However, after moving to the United States in 1939, he became an influential figure in American literature as well, embracing and contributing to the literary traditions of his adopted country. Thus, his work is reflective of the cultural milieu and literary traditions of both England and America, granting him the designation of an Anglo-American poet.