The only "federal" roads I know of are the ones on the Interstate system. What about the parts of the Interstate system where tolls are collected by the state? And are there any "federal" bridges or tunnels?
So the federal highway system are the roads with an “I” in front of them, ex I-95. Those are funded with federal money. Sometimes those roads run through state “exchanges”, meaning the state worked something out with the feds to run the system through a state road for a few miles for whatever reason - Maryland has a lot of exchanges - those are the state. Typically with build projects like bridges and tunnels, the Fed’s fund the build and states (or multiple states) fund the upkeep. I only made the point because this stuff can be confusing to a lot of people. They think the Fed’s are responsible for their local, county or state roads and it’s not true. Although, the Fed’s have gotten into local aid to sort of improve economic and quality of life transportation on limited basis.
Under or during Clinton, the feds created/designated the National Highway System that includes pretty much all of the major highways that are needed to keep the economy going and the country functioning. It does not include the jungle of county roads and purely local routes but could and does include some if their is a strategic reason for it- but is majorly extensive, well beyond the interstate system. The idea that the feds created the interstate and then all the rest is state and local is okay for simplified model but when you lift up the hood, it is well beyond that. So if the road is designated as part of the National Highway System there are all sorts of federal funding and perks that go with that. Although the funds go through the states. No punchline here. Just sayin that when it comes to fed highway planning and funding it is more than just the interstate. https://en.wikipedia.org/wiki/National_Highway_System_(United_States)