The price of gasoline has gone up around 50% in the United States since the war in Iran began, but that average can mask big differences across the country. A gallon of regular fuel cost $4.54 on Wednesday, according to the AAA motor club. But in California, gas averaged $6.16, while it was just $3.96 in Oklahoma. Within those states, prices at the pump differed greatly from county to county and city to city. More than half of the price of gasoline is tied directly to the price of oil, according to the Energy Information Administration, a federal research agency. Since the United States and Israel began attacking Iran on Feb. 28, the price of a barrel of Brent crude, the international benchmark, has risen more than 50%. Much of the state-to-state and city-to-city variance in the price of gas has to do with the location of oil refineries, the logistics of getting fuel to the pump, state taxes and regulations, and competition among gas stations. It costs a lot to transport gas A significant share of U.S.…