United States dollar will not fall. The currency did not fall even during world war two.
I don't believe the US currency will fall, but the situation now is differnt from WW2. While Europe was buring, the US was still intact. They provided supplies for the rest of Europe, mening their currency was the dominate during that time. This is a differnt scenario where they are in direct conflict with another country.
The reason the US dolla will not fall is because the country would not be attacked directly. The proof of this is that the US dolla fell against major currency after 9/11 attack. If Iran's attack where directly on US soil and not military bases, the currency would have fallen.
Also, if the US truly has control of Venezuelan oil now, that mean oil prices going up might favour them.
That being said, "it would not fall" doesn't mean it will not drop at all. The US dollar has already see a slight drop recently and it will still drop but it won't be a significant drop.