I would expect that the taxes on gasoline would be higher in the northern states because of all the winter weather (snow & ice) that guzbuck up the pavement. Plus the road salt I hear they use eats away the bridges by accelerating the rusting of the steel reinforcing in the bridges.
Down here we don't have the harsh winter conditions and so we don't have to replace pavement and bridges so often. About the only place we really ever get "winter" conditions is up in the "panhandle" of Texas which is a very small area in relation to how large Texas is total area.
Not to say our government rips us off, they just do it in other ways here, and it is everyday as well.
Thanks for the great information in your comment and the support, very much appreciated!