Give U.S. citizens wishing to secede a large area of public land for them to settle on - all in one place, allowing remaining non-seceding citizens of their respective states to remain part of the United States.
This will allow the majority of people in many states to continue enjoying their rights to maintain U.S. citizenship, and allow the secessionists to all get together in their own new 'nation,' from which they can apply to the United States for Foreign Aid, to assist them in surviving without all of the benefits of U.S. Citizenship.
The only condition to this land grant and possibly getting foreign aid would be that they build a secure wall to protect the U.S. from illegal immigration of citizens from their country to ours.