Apple watch carries international warranty

Depends on the type of watch.

For GPS + Cellular Apple Watch warranty is only valid in the country of purchase due to region specific cellular hardware in the watch.

For the GPS only watch (not cellular) it should be possible, but its at the discretion of the Apple Store or Authorized Service Provider in the country where you are seeking warranty service.

Here is Apple's warranty....https://www.apple.com/legal/warranty/products/warranty-us.html