This is going very tangential, but no, not all bridges are directly paid for only by people driving on them.
To make public bridges into an ISP analogy, imagine: municipal and state taxes as well as tax revenue from other states (via Federal highway dollars) pay for a municipal broadband network. You may or may not actually use the service, and you pay for it either way. You likely don't have any other choice of ISP. And it's not-for-profit, and the general public and lawmakers constantly clamor and legislate for better service at lower prices.
Although not true, I always liked to think that taxes on my vehicle, fuel, and tolls paid for the infrastructure upon which I drive. I have no idea whether those are sufficient, but I'll bet in my state they state of high taxes and crappy infrastructure they are more than enough.
Generally, the taxes and tolls levied on drivers only pay for ~50% of US road spending - the balance comes out of the general tax pool on both drivers and non-drivers, so it's (arguably) heavily subsidized. (But one could argue that non-drivers benefit from the road system in terms of things delivered to them by truck, etc.)
To make public bridges into an ISP analogy, imagine: municipal and state taxes as well as tax revenue from other states (via Federal highway dollars) pay for a municipal broadband network. You may or may not actually use the service, and you pay for it either way. You likely don't have any other choice of ISP. And it's not-for-profit, and the general public and lawmakers constantly clamor and legislate for better service at lower prices.