If a company whos main office is located in Kentucky has various other locations in other states, WV, FL, IN, etc....they put a cafeteria plan into place and offer to all employees eligible in all locations, is the cafeteria plan governed by ky law since that is the main office or do all of the states apply and you need to find out how the states differ to manage the cafeteria plan?

To the extent that ERISA does not preempt state law, then you'll need to deal with each state's differing payroll and insurance laws for the employees' whose employment is in that state.