Can I still file a FAA Domestic flight plan?

No, the FAA Flight Service transitioned to mandatory use of the International Flight Plan format for domestic and international civil flights on August 27, 2019. With the exception of military flight operations, the international format is required for all IFR and VFR flights across the NAS.

The FAA will accept a flight plan in the international ICAO format for IFR, VFR, SFRA, and DVFR flights.