Applecare is an extension of the original warranty, but the original warranty is extremely restricted outside the country of purchase:
http://www.apple.com/legal/warranty/products/iphone-english.html
"IMPORTANT RESTRICTION FOR iPHONE AND iPAD SERVICE.
Apple may restrict warranty service for iPhone and iPad to the country where Apple or its Authorized Distributors originally sold the device."
In fact you may find even if you are prepared to pay for a repair Apple will not repair certain devices (likely anything with cellular capability) from one country in another country. Often Apple does not actually repair a device but simply gives you a refurbished unit that is identical to the one you bought. However, a model from one country may not be available in another.
I advise against you buying a phone for him in the USA. There can be other issues too:
LTE Find the right iPhone for the right country or region. - http://www.apple.com/iphone/LTE/