States and regions have created their own independently-operated electronic highway toll systems. In the Northeast, "EZ-pass" has been adopted. In Florida "E-pass" is used. In Colorado, "Express Toll" system is used. In California... you get the idea. Our nation should encourage states to honor toll-collection transponders from other states.
My phone connects to any wireless network around the world. Why can't I use my own toll transponder when traveling in the US? Passing through a toll plaza without a transponder (or not having the right change at unmanned plazas) incurs a huge penalty. And the penalty can be compounded if the car is a rental when the car company tacks on administrative fees.
Create a way for all states to utilize a nation-wide electronic highway toll system.