Not sure if you're talking about getting a FAA (US) CFI (Certified Flight Instructor) or a EASA FI license. Anyway, in order to get a FAA CFI you need to hold a FAA CPL. Below I've attached a few schools in the US which provide training for both FAA and EASA.
https://www.flyeft.com/easa-flight-instructor/
Florida Institute of Technology
FAA + EASA with ATPL Course Flight Training USA
JAA/EASA Airline Pilot Course | Skymates, Inc.