Certain schools will and certain schools will not accept foreign students for a CFI course.
Keep in mind that a school is a business and not a charity.
Nobody will provide you with a F1 visa if you only do a CFI course.
The more training you do ( and pay for) the more willing they will be to help you.
Smaller schools will not have the authorization to apply for a F1 so you're stuck with the big ones. Aviator, FlightSafety, Embry Riddle and maybe Phoenix East out of Daytona