Yes - you still have an obligation to file your U.S. federal return, even if all of your foreign earned income is excluded via the foreign earned income exclusion reported on Form 2555, Foreign Earned Income.
Per the IRS: "Since the foreign earned income exclusion is voluntary, you must file a tax return to claim the foreign earned income exclusion. It does not matter if your foreign earnings are below the foreign earned income exclusion threshold."
Please see the following IRS Frequently Asked Questions (FAQs) About International Individual Tax Matters"
https://www.irs.gov/individuals/international-taxpayers/frequently-asked-questions-about-internation...
