It's a world market. US as a producer sells oil both domestically and abroad. US as a consumer consumes both domestic oil and foreign oil. In 2018, it worked out to about 9.9 million barrels/day of foreign oil being imported, and 7.6 million barrels/day of US oil being exported.

If something disrupts production of some major world exporter X, causing the world market price to rise or causing shortages on the world market, US domestically sees that too.

So does Iran - if the price of oil goes up they pay more domestically as well. As it happens they subsidize the price of energy internally but that brings more problems then it solves.