I live in Europe and have never owned a car in my life. I don't even have a license. Overall, I like how things are handled here

Here in Denmark it would be around $95 to fill your Miata. Assuming it has a 45l tank.

To be fair, the US also has very low rates of gas tax compared to other OECD countries

Assuming a 45 liter tank you'd spend €84.60. Mind that a LOT of that is tax. If you strip off Value Added Tax -- equivalent to sales tax if I understand correctly, though a fair bit higher -- you'd pay €70.50. That still leaves excise tax, which is levied specifically on goods the government wants to discourage. Cigarettes, Alcohol, Gas. Without that you'd pay €34.99.

I'm not sure how the tax breakdown works in Texas, but I'd not be surprised if it'd be one of the main drivers of the price difference.

High, mainly because of high tax rates. This is a good thing, because it reflects the social cost of carbon (plus pollutants, road-building, and other externalities). https://theconversation.com/what-is-the-social-cost-of-carbo...