President Trump is pitching a U.S. naval blockade of the Strait of Hormuz as an opportunity for American oil-and-gas exporters. The squeeze on supplies is a bad omen for prices at the pump. The U.S. plan to wrest control of the key waterway from Iran would potentially cut off the roughly 2 million barrels of oil that Iran has continued to ship through the Strait each day, most of which was headed to China. With 20% of the world’s daily supply of oil and liquefied natural gas already trapped behind the Strait, Japan, South Korea and other Asian countries that rely on…