Does the mere ownership of a US bank account that earns some interest require a non US person (say, based in Europe, EU in particular) to file a US tax return? Are there any other reporting requirements that may be triggered by such a bank account? I know e.g. that FATCA form 8938 is part of the federal income tax return statement so if a person has to file US taxes presumably they also have to complete 8938 which can be costly and require the services of an accountant to ensure that no mistakes are made. I am basically trying to figure out whether a US bank account is worth the hassle for a non US person. I am currently in the US but if I ever return to Europe I would need to decide whether I should keep some savings in the US (for diversification) or whether I should simply close all US accounts and wire everything to the EU.
In general if you are not a US citizen or tax resident alien and have US-source income, you need to file form 1040NR (or 1040NR-EZ) and pay tax. However, interest on bank (and credit union etc) accounts is excluded; see section 3 of pub 519 (website is currently still 2017 version, and with the shutdown may not get updated soon, but TTBOMK this area hasn't changed; also available in PDF, see https://www.irs.gov/publications ). Assuming you have no other US-reportable income, you don't have to file.
The bank will probably require you to provide form W-8BEN to establish that you qualify for this exclusion, but that is with the bank only and is not filed with IRS. Some US banks may not want to establish accounts for nonresidents and/or non-SSN-holders (and you aren't eligible for SSN) because it complicates their compliance, but that's also between you and the bank.
Even if you were required to file an income tax return (and possibly pay), as a non-resident alien you are not required to include form 8938. From the instructions:
You are a specified individual [and must attach 8938 to your return if any] if you are one of the following:
A U.S. citizen.
A resident alien of the United States for any part of the tax year (but see Reporting Period, later).
A nonresident alien who makes an election to be treated as a resident alien for purposes of filing a joint income tax return.
A nonresident alien who is a bona fide resident of American Samoa or Puerto Rico. See Pub. 570, Tax Guide for Individuals With Income From U.S. Possessions, for a definition of bona fide resident.
And finally, although I'm not subject to 8938 (or FBAR either), I've looked at them, and they don't look to me any more difficult than the forms I do fill out as a native, and I wouldn't use a CPA for them. But that's a subjective judgement and YMMV.
In general you don't have to file a tax return unless you make more than a specific threshold. I believe that threshold is the same as the standard deduction, which will be $12,000 this year (FY 2018).
If your income purely from interest in a bank account exceeds $12,000 you have made mistakes elsewhere.