The US doesn't have a refinery capacity problem at the moment. It has in the past, for example May 2007, when gasoline prices averaged $3.15 a gallon, at a time when oil was about $64 a barrel.
May 2007, of the $3.15 for a gallon, $1.45 went to pay for the crude oil, and 88c went to pay the refiners.
This April, the latest figures the DOE have published, with a gallon of gasoline at $3.46, $2.52 paid for the crude oil, the refiners got a little under 35c.
The current price of gasoline has everything to do with the price of oil, and nothing to do with refinery shortages. In fact, US refiners have been cutting back production earlier this year because of weak demand.