My money says Trump is speaking for the benefit of the Iranians. The President very carefully left the door to continued negotiations open. Therefore, this is not a declaration of war but a warning, a spanking, designed to drive Iran back to more reasonable negotiating postures.
Brother, we have seen this movie MANY times before ... and it *ALWAYS* ends the exact same way. There is nonegotiating with Islamists, NONE. They practice taqqiya, therefore the ONLY reasonable posture is annihilation.