Yes, it is acceptable to file an amendment for this reason, even if the financial totals don't change. The IRS allows Form 1040-X to be used specifically to "correct" information, not just to change dollar amounts.

The EIC does show the IRS knows the residency requirement but the lawyer's concern over a box makes it smart to affirm residency and check the box. 

Green Card Holders: For clients with specific residency restrictions or 72-country restrictions, having an "affirmative statement" on their tax record (like this checked box) can be helpful evidence of their physical presence in the U.S.

For the explanation, focus on the informational correction.

For example:

This amendment is being filed to correct an administrative omission on the original return. Specifically, the box in Part IV (Earned Income Credit Information) confirming that the taxpayer's main home was in the United States for more than half of the tax year was inadvertently left unchecked. There are no changes to income, deductions, credits, or the total refund amount. This filing is for informational purposes to accurately reflect the taxpayer's residency status for the 2025 tax year