When market logic trumps politics, this is what happens. Refineries need feedstock. They do not deal with politics. They deal with demand and supply. And because of this, the United States has been importing Russian oil for years, as strange as this may seem in the current political situation.
"Trump cancelled the Iran deal because a different group of billionaires are now in control of the White House, and of the rest of the US Government. Trump’s group demonize especially Iran; Obama’s group demonize especially Russia. "