The oil imports of the USA have declined strongly over the last past years because the domestic oil productions increased massively due to fracking. Therefore the States are not longer dependent from oil imports than it was before fracking starts. You can also see this in official figures published on
https://www.eia.gov/energyexplained/index.cfm?page=oil_importsTrump 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.