Davidathomas42
If you go around calling yourself a 'CFI' when you are a mere FI(R), you won't be particularly popular.
I think that the above response says quite a lot
Don't worry about terminology some instructors can't accomodate international terminology because they have a strong dislike of all things foreign.
Most people know what an FI is and the US CFI is well understood by most internationally minded flying schools. There are a few pedants out there but you will never convince them that you can fly an aircraft and teach their students because they view the world of flying through a prism that cannot accomodate the wider world.
Anyway you will be a MERE FI (R) How dare you pretend to be a CFI !!!