That's a very good question. It seems that we have outgrown the need for individual states, besides of course, for more serious local questions of whether or not, we can have legal fireworks. dws
States are responsible for local tax rates in order to pay for local civic improvements, such as schools, roads, and other necessities which may be needed on a "local" basis.
IMO, in today's world environment, states have become, in the grand scheme of things, the same kind of local status as cities/counties/townships. They are still needed for local governance and administration, and establishing tax rates for local needs, but not for national governance. But, they should guarantee an individual's rights on a national level. They should not undermine an established national right.
And while we are at it, let's do away with the electoral college and make all national level elections a true "national election" aka, the popular vote . That would make national elections a true representation of who The People would want to represent them instead of the results of half a dozen or so of "Swing States". It would make presidential candidates campaign in all 50 states. We can still "locally" elect representatives and senators to look out for our states' interests in the "national" government. I think that is the way our founding fathers would have really wanted it, especially since the abolition of slavery and the abnormal effects that slavery (3/5 of a person, e.g.) held over our electoral processes and national representation in Congress.