Sure..
Why not he was Afganie and saw his country being attacked by people he thought had not right attacking his country.
Yep but the boy wasn't
Alright, I don;t think it was an inside job, I still don't feel bad for anybody I don't know, and it sure doesn't sound like a good reason to attack a whole country.
Ok, so he was Afghani and saw his "country" (he was actually Canadian, born and raised there). Ok fine, we'll look at it that way. Then I guess it's ok that he was picked up on a battlefield killing Americans. That's the price he paid. At 16 he's old enough to know the consequences of throwing a grenade at soldiers.
Secondly, it's a plenty fine reason to attack a whole country. The Taliban were financing, aiding and giving Al Qaeda quarter in their country. They allowed training camps, access to weaponry and a spot for them to plot attacks against the West. Not only that, they were an oppressive regime that drove their country into the ground. They had what was coming to them.
Not only that, but now they're invading from Pakistan with Pakistani fighters trying to retake a country that's not theirs. They kill civilians and have become invaders themselves.
Not only that, there are dozens of countries in Afghanistan. Why don't you go tell Merkel how upset you are with her.