Answer:
See below
Step-by-step explanation:
Simply speaking, if we did not have states, the United (country?) would not be a democracy and rather controlled executively by a single rulor or president. Instead of each state having its own power, the whole country would be unified as one. It may still be a free country, however, more power is granted to a single person, rather then each state representing its people, thus creating a well distributed balance of power.
Hope this answers your question.