Iran: We can beat the USA.
Japan: You do realize we beat him in Battleship, and he dropped the sun on us.
Iran: So?
Japan: Twice!
Listen here, you dum-dum. The joke is about Japan reminding Iran that the US is not someone to mess with. Japan already fought the US, and the US dropped not one, but TWO atomic bombs on them! And you wanna pick a fight? Sheesh. Some people, am I right?