A) That's a BIG if.
B) Even if true, it's not an act of war against the US.
C) It's only our problem if we make it so and, at the moment, I don't see the need.
:-)
The United States — like it or not — is the guarantor of world trade. It will react if international law is contravened in the Gulf, the Strait of Tiran, Red Sea, Suez Canal, South China Sea, Straits of Malacca, etc. It is also now the guarantor of the world-wide energy market. Now the only way out of this situation is a return to true isolationism, and economic autarky. And that would be a disaster for both the United States and the world.
For reasons of its own, Iran has been egging-on the United States and Europe. It may have something to do with the Shiite’s own end-of-the-world view, or more precisely it may be that a crisis is needed because the Iranian suq is ready to explode, just as it did when the Shah was overthrown.
In any cas, next stop: UN Security Council.