There isn't that much of a difference, IMHO. "Patriotism" is just the result of getting lots of PR about your country being the greatest getting heaped onto you and starting to believe it. If you just embraced the professed values of your country, there would be no need for patriotism. You can fight for them anywhere, anytime, regardless of your passport.
It expresses much of the same commitment as joining the army, just in another way. Young hotheads are more ready to die gloriously for their cause, while the more level-headed fellows rather live humbly for it.