You can ship internationally with USPS via First Class Mail International, Priority International, or Express International. Out of those 3 only Express Mail comes with tracking. The other two do not. To attach tracking on them you have to send them as "Registered Mail" which means paying postage cost and on top of that adding a fee for the registered mail title.
Registered Mail fees cost $10.95 and above. The fees are based on the declared value so the more expensive you value your item at, the more it will cost to have it be sent out as registered mail.