“The states, just like the fed already does, can add paperwork though. “
Indeed. But to my knowledge no state (or the Feds) PROHIBITS the USE of cash based on the amount.
That’s because they’ve learned they don’t have to. They can make it irritating, and that’s much more effective. People do prohibited things all the time, people actually try not to do things that irritate them. Also of course keep in mind that all these regs are tied to the drug war and having a lot of cash on you has been declared automatically suspicious and can get you searched (and before you ask how they can tell remember money has magnetic strips and every facility the government secures has metal detectors) and questioned and the money confiscated. Why prohibit when you can confiscate.