They can will it to be a user fee all they want, but it isn't. As an example, during my time in Austin I drove quite a bit around town if I wasn't on the #1, 5, 7 buses. But for the most part I wasn't on the highways. A little Mopac here, a little 183 there, but maybe twice a month during school if that. TxDOT and the MPO get back federal flex funds which they can use for lots of things. But it's not usually paying directly for what you're using that gas on most, those local roads.
Now it does come back to transit etc, but you're not paying directly for what you're using. I do pay a user fee now when I go over the bay bridge to my Gramma's house. And for the most part that $4 charge keeps me taking BART, which is faster anyway to downtown Oakland. But these tea party cries of socialism fall on deaf ears when you know these same people LOVE the socialism of roads. They even love the community good of transit. So much so that when it doesn't work, they get angry that government isn't doing a job they didn't fund it enough to do. Oh the irony.