Or, phrased differently...
Generally, a "license" or a "certificate" issued by the national government is internationally accepted by most other governments by reciprical agreement. If this was not the case, the world would just never get anything done! Again, generally, these licenses and certificates conform to internationally (ICAO) agreed formats and standards. Hence their ready acceptance.
"Permits" on the otherhand, should be thought of as a permit to do something (fly a plane, in this case) without conforming to all of the (ICAO, in this case) requirements for that activity.
So, another nation might allow you to exercise permit privilages in their airspace ("experimental" transborder flights, for example), but are not internationally required to allow this. It is likely that where one nation does not have an equivilent permit privilage themselves, they would not rush to accept another nation's privilage.
Be patient, 17 is not that far off. Many of us had to wait to be old enough. You still have the opportunity to fly by yourself under "supervision", and that is quite fair. Your prospective passenger will be very pleased that you took the extra time, to get that little extra experience. It is their life you take with you to the sky, make sure you are very prepared for that great responsibility!