The United States is exporting crude at record levels as the world grapples with an unprecedented disruption of Middle Eastern supply. U.S. oil has become the supply of last resort—and it is not infinite. U.S. crude oil exports since the start of April have been running at 5.2 million barrels daily, data from Kpler showed earlier this week. “It's a constant parade of tankers coming in and out,” the chief executive of Corpus Christi port in Texas…