That's precisely what Al Qaeda wants the world to believe.
It's not believable, however, prior to Iran getting the bomb, and even then, Iranians are Shi'ia Persians who disagree with most everything about Al Qaeda's Sunni Arabs.
This is not to say that Iran is a good guy. The Mad Mullahs are their own special breed of evil, and are most certainly our enemy.
...But it harms our own efforts to blindly lump our enemies in together. They are different. They require different approaches and different timing...something that lumping them together into one giant war would complicate.