I think you are wrong about this. My belief is that that most states use "conventional" gasoline, a substantial subset require the same "reformulated" gasoline, and a handful only allow the sale of "boutique" formulations in all or some of their counties.

Here's a list of the states that require reformulated: https://www.epa.gov/gasoline-standards/reformulated-gasoline

And here's a shorter list of those with areas requiring boutique formulations: https://www.epa.gov/gasoline-standards/state-fuels

My belief is that all the rest only require the basic federal standard, which results in a map like this with a lot of states in gray: https://www.eia.gov/todayinenergy/detail.php?id=67464

But if I'm wrong, I'd love to be corrected. What do you have for sources that support your assertion that "every state has their own gas"?