Regarding international warranty

There is NO international warranty. If you buy the phone in the US and have an issue with the phone, you will to return to the US with the phone for service. You can't even ship it to Apple as Apple doesn't accept international shipment.

Buy your phone in the country you live.

There is no international warranty for Apple devices that have a cellular radio. You might be able to get service for small issues or possibly a screen replacement (that is at Apple's discretion) but you will not be able to get the iPhone replaced if you have a significant hardware problem.

There is no international warranty on any Apple hardware.