Remove all federal laws. Allowing each state to govern themselves. Allow the use of the American Dollar to be used in any and all states, and allow any citizen in the current US to freely travel between states.
Enforcing a law that works much like the European VAT laws.
This should be taken very seriously in the attempts to prevent a possible civil war. And to prevent some states gaining enough wealth to buy out other so called ex-states, which will eventually result in the US being a whole again with the same problems 200 years down the road.