Hi LSAT4Life! Thanks for your great questions, and happy to help
Answer choice (B) is actually incorrect for a different reason. Answer choice (B) contends that Lum's poetry expresses a conflict between two things: 1) a desire to participate in a community with shared values/traditions; and 2) "a desire for individual success." Lum's poetry does express a conflct between "heritage and local culture" (as explained in the last paragraph of the passage), but "desire for individual success" is actually discussed as an attribute of US culture in the last paragraph of the passage. Although Lum considers the conflict between his heritage and local culture in his poetry and this desire for individual success is part of his local culture, this would be an indirect connection between the passage's main point and the main point as described in answer choice (B). For a main point question, we want direct support from the passage when we select the correct answer choice. This more tenuous connection leads answer choice (B) to be incorrect.
I do want to point out, though, that a frequent type of incorrect answer choice for main point questions is one that mentions an aspect of the passage but is too narrow in scope to capture the main point, as you mentioned in your question. So great job being on the lookout for this type of incorrect answer choice!
Let's turn to why answer choice (A) is the correct answer choice. The beginning of the first paragraph of the passage explains that Asian American poetry from Hawaii usually falls into two categories: 1) poetry that portrays a "model multicultural paradise," or 2) poetry that exemplifies traditional Asian American literary themes. The author then goes on to state that Lum's poetry is unique because it "demands to be understood on its own terms." The rest of the passage goes on to characterize Lum's poetry, discussing in the second and third paragraphs how he portrays the conflict between his heritage and local culture.
The first thing we want to look for in a correct answer choice is that it characterizes the fact that the author is trying to show why Lum's poetry is unique. Answer choice (A) does so, whereas answer choice (B) does not. Answer choice (A) also correctly describes what makes his poetry unique.
In terms of the phrase "search for a new local identity," several lines in the second and third paragraphs support this assertion. In the second paragraph, for example, the author discusses how the speaker in one of Lum's poems realizes the need for a "new identity" that is "sensitive to its new environment." This assertion is also supported by the first line of the third paragraph ("complex relationships between heritage and local culture in determining one's identity") and the last line of the third paragraph ("in ways that allow for a healthy new sense of identity to be formed").
I hope this helps, and please let me know if you have any other questions!