Trump should make sure that the sanctions does not result in a decline in the Iranian crude production. Else it will affect the Americans more than anyone, since they are among the top importers of crude oil.
It wouldn't have that much of an impact. There is a lot of shale production capability sitting idle in the US, so if Iranian oil was taken out and prices rose, it would put some of that US capacity back to work, and the prices would come down again. I also suspect that Iranian reductions would cause other OPEC producers to seize the opportunity to increase production, since they all only begrudgingly agrees to a superficial cut anyway. Long story short, I wouldn't expect anything Iran does with oil to have a big and lasting effect.