If you were not a US resident and your only income is interest from a US bank and not related to running a business in the US, you do not need to file a 1040-NR.
Why? Because the tax code says so in I.R.C. 871. https://www.law.cornell.edu/uscode/text/26/871
U.S. Code § 871 - Tax on nonresident alien individuals
(a)Income not connected with United States business—30 percent tax
(1)Income other than capital gains
Except as provided in subsection (h), there is hereby imposed for each
taxable year a tax of 30 percent of the amount received from
sources within the United States by a nonresident alien
individual as—
(A)interest ...
(i)Tax not to apply to certain interest and dividends
(1)In general
No tax shall be imposed under paragraph (1)(A) or (1)(C) of
subsection (a) on any amount described in paragraph (2).
(2)Amounts to which paragraph (1) applies
The amounts described in this paragraph are as follows:
(A)Interest on deposits, if such interest is not effectively
connected with the conduct of a trade or business within the
United States.
(3)Deposits
For purposes of paragraph (2), the term “deposits” means
amounts which are—
(A)deposits with persons carrying on the banking business,
(B)deposits or withdrawable accounts with savings
institutions chartered and supervised as savings and
loan or similar associations under Federal or State
law, but only to the extent that amounts paid or
credited on such deposits or accounts are deductible
under section 591 (determined without regard to
sections 265 and 291) in computing the taxable income
of such institutions, and
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