Homekit is not region bound. So long you have the right hardware, it works.

For your case:
Smart thermostat read room temp. When certain temperature reached. It then trigger your Aircond to turn on. If your Aircond is smart to talk to your thermostat that's it. Else you will need a RF/IR blaster device that act as a middle man to turn on your Aircond and set to right temperature.

For simple setup like this, you don't really need the hardware to be HomeKit compliance.