Back in the 70’s Carter told all the states that if they didn’t adopt a 55 mph speed limit, they would lose their funding. States didn’t seem to complain too much then.....and that actually was a stupid edict from up high.
The Federal government had the authority to impose a national speed limit on highways that qualify for Federal funding, but they couldn't force the states to actually go out and enforce those speed limits. This is where the states and cities have a legitimate point regarding illegal immigrants. They are not immigration enforcement agents, and cannot be deputized against their will by the Federal government.
We may not like the results, but this is the exact same argument that has been used successfully in the past by state and local police departments who had no interest in enforcing stupid Federal gun laws.
Louisiana refused to comply, and when the funding was cut off they ceased maintenance on the interstates.
When I was stationed at Keesler, the interstate along the gulf coast had grass growing up through cracks, and there were a few four way stops with traffic lights as well. I wish every state had done that.
I remember those days. I was driving between Ely and Las Vegas NV going about 85 MPH when I was pulled over by the NV Highway Patrol. The officer informed me that I was speeding and asked if I saw the speed limit sign that said the speed limit was 55 MPH. I said “no sir.” He told me it was 40 miles behind me. He then said “slow down and have a nice day.”
That issue alone was enough to give us Reagan. Cost to Trucking industry was tremendous because the truck drive train was not efficient at 55.