It actually really isn't. First you have refinery setup. You could give Houston refineries middle east Sour Crude for free - that are set up for light sweet shale crude, it would take them a year and millions of dollars to switch over.
You also have transportation. West Coast refineries still refine middle east oil because its cheaper for them to get that than ship shale over the rockies or through the Panama Canal - since there is no pipe.
Finished product is shipped from the US more frequently - we were shipping a lot of diesel to Europe when the Ukraine thing started. Not sure anymore.
Here is a chart of the world oil flows.
https://www.eia.gov/international/c...ld_Oil_Transit_Chokepoints/images/figure1.png