apple care is valid worldwide?

No. Apple Care+ is only valid in the country of purchase of the device it was purchased for in the case of iPhones, iPads, and Apple Watch.

http://www.apple.com/legal/sales-support/applecare/applecareplus/docs/applecarep lusnaen.html

4.1 Hardware Service and ADH Coverage Area. Under AppleCare+ for iPhone, AppleCare+ for iPad, AppleCare+ for Apple Watch, Apple may restrict hardware service and ADH coverage to the country where the Covered Device was originally purchased.

the standard warranty is valid only for the country you purchase your iOS device in, you are "out of pocket" for repairs to the device when in warranty but out of country of purchase for that but Apple Care for iPhone does show a clause about you (the onwner) responsible for out of country mail in repair service if applicable, which could mean one country can't get parts and you facilitate it that way, or there is no problem and you can do it.

http://www.apple.com/legal/sales-support/applecare/applecareplus/docs/applecarep lusnaen.html

Honestly I'd call Apple

1-800-MY-APPLE