The US does not import much refined product. Foreign suppliers are not encouraged to divert shipments of refined product to the US, as very few refineries abroad even produce the gasoline formulations required by law in this country.
If there is a shortage in the US, prices will rise and encourage suppliers who otherwise would be shipping to other countries to divert product to the US. Gasoline isn't the only refined product. Also, Venezuela does ship quite a bit of refined gasoline to the US. It's the fault of clueless politician who campaign on the basis of slogans and photo ops for pushing their states to enact niche product reguations for their states. I bet there's a zero or even negative environmental benefit from those requirements. The ethanol requirement absolutely causes environmental degradation. It takes more energy to plant harvest, transport, and distill enthanol than is recovered from burning it as fuel. The extra acreage planted to produce grain for ethanol increases erosion and depletes topsoil.