How could the FBI Possibly be Involved in This Plot?

At the start of the film the FBI calls Seagal's old boss at the "Tokyo CIA Headquarters" and asks for his help because they think that the assasaination of the politician might be "terrorist related." OK, I don't know--MAYBE there is an official Tokyo CIA headquarters. Could be. But why would or could the FBI be involved in terroist activities outside the USA? They are strictly internal.

Yet, when Seagal (who is actually CIA) investigates, he pretends to be an FBI agent, and all the local Japanese authorities act like that means something in Japan, as though Japan is an American territory, like Puerto Rico.

Did anybody else find this confusing and/or stupid?