A foreign-owned single-member US LLC with zero income, zero expenses, and zero US activity in a given year still has a federal filing obligation. The IRS requires a Form 5472 and a pro forma Form 1120 annually to report ownership and any reportable transactions. This requirement was made permanent in 2017 and applies to LLCs that have never traded.
State-level annual reports and fees also apply regardless of revenue in most US states. A company that has sat dormant for three years with zero activity and zero filing has accumulated $75,000 in potential IRS penalties before a single dollar of tax is owed.
Full details on these filing mechanics are in our guide on US Taxes for Foreign-Owned Companies.