If the discrepancies between state policies were large enough, I imagine you'd basically see white flight on a national scale. Essentially, supporting any type of social safety net would be optional for the people with the resources to move out of state. As a result, middle-class and wealthy people would flock to low-tax states without expensive social programs, leaving behind a higher concentration of needy people in the states with the stronger safety nets. What social programs remain would presumably go bankrupt while the nation's wealthiest individuals basked in the glory of their virtually tax-free lifestyles.