"English (America)" refers to the use of American English in this paper, which is a language variety of English, different from British English. This means that your teacher thinks that you have used some expressions in your paper that are not in line with American English language norms and need to be revised and improved.

To improve this situation, the following measures can be considered:

Understand the language norms and expressions of American English and compare them with British English. You can refer to some official language norms, such as the American English Guide.

Carefully check the language errors in the paper, such as spelling errors, grammatical errors, punctuation errors, etc. , and make corrections.

Adopt expressions that conform to American English norms, such as using correct vocabulary, grammatical structure and common expressions.

Seek the help of professional language editors, let professionals polish and modify your paper, and ensure that your paper conforms to the language norms of American English.

Finally, you can improve the language quality and expressive ability of the paper by carefully reading and revising the paper and following the language norms of American English, so as to better demonstrate your research and thinking ability.