Which, first of all, you already do, the county/state/federal laws apply on top of those.
But you're also assuming that uniform national laws will be less complicated than dealing with different local laws, which doesn't seem to bear out in practice. California is going to care about earthquakes and Massachusetts is going to care about ice storms but not really the other way. If you do business in both California and Massachusetts then you have to care about both earthquakes and ice storms regardless, and if the relevant legislation is at the federal level then it will cover both. Which means local laws aren't more complicated for companies who do business in both places, they're less complicated for companies who don't, because then if you only do business in Massachusetts you don't have to deal with earthquake regulations.
Sure they do. You're insuring against earthquakes in California and ice storms in Massachusetts. North Dakota has a much different banking environment than New York City. Trucks pulling three trailers make sense in big empty western states with wide open spaces but no sense in high traffic urban environments with tight corners.