The source of the oil used to make gasoline is going to be mostly dependant on where you live in the US. If you live in the coastal regions, chances are the gasoline is made of imported oil. That's just the way it is.
If wanted a "nitrogen enriched" gasoline I would buy a bottle of Techron concentrate or any other PEA based cleaner. That's going to be much more effective dose, than the low levels of additives in road gasoline.
For me the issue with Shell Oil/Products is the companies ongoing operations in Iran, even though they are not importing that stuff as raw materials to the US.
It would be nice if there was an oil company which advertised 100% US or North American Gasoline. I would be willing to pay more for that, vs making some saudi prince that much richer. .