Some ninjas create a way to travel between worlds and accidentaly come to ours inside a militar base. They run back to the portal but are unable to close it. Obama then suspects of an interdimensional invasion and assemble the army to atack, defeat and kill all the aliens from the other universe. Whomever the military will discover they are ninjas. And ninjas... well.. they are ninjas! Who wins?
-No ninjas in naruto verse posses imortality. Neither Pain or katsuki members.
-USA military posses all soldiers and equipement ever.
-All ninja tribes and Akatsuki fights.