EASA FI to FAA CFI
To hold a FAA CFI you are required to first hold a stand alone FAA CPL/IR or ATP. In order to then obtain a CFI, you will need to complete the CFI and FOI knowledge tests. For the checkride, you will be required to complete a minimum of three hours flight preparation with a FAA CFI and be signed off for the checkride. There's probably quite a few manoeuvres you haven't flown if you haven't been involved with the FAA before, such as chandelles, lazy eights, eights on pylons, turns on a point etc. that will require some flight training before your CFI checkride.
Then, complete the CFI checkride with a FAA Inspector. Repeat the process for CFII and MEI (but can be a Designated Pilot Examiner for second and subsequent CFI checkrides) if you wish to add those privileges.
Probably not the answer you were looking for... That's without mentioning US VISAs and TSA.
ifitaint...
EASA FI and FAA CFI/CFII/MEI