I always consider people who are part timers and/or not under permanent allegiance of the particular nation as mercenaries regardless their motivations are. Also, everybody needs money and everybody is motivated by money at some point. Sure, I could just go out there and claim that I love USA but why? It is because its rich "land" which translates to money. All the "mercenaries" who crusaded weren't of French or whatever. They were Genoese or whateverese. Basically your daily policemen, firefighters and coastguards are not mercenaries. So if US pilots are gun down, fallen onto desert and hiring a noble camelman of Syrian Sultanate to guide them or work with them, that is your mercenary. That's just me anyway.