Answer:
American writers often write about the topic of American identity.
Step-by-step explanation:
The first one is rather extra, and there was no mention of poets or novelists in the sentence in the question.
The second one is nearly right. But the question mentioned "academic vocabulary", and being is less appropriate than identity.
The third one is correct. It has the same meaning and while it replaces words, it creates no new words of its own.
The last one kinda doesn't make much sense.