The US government is and was established on the basis of a centralized power that controls a nation with rules and policies that act in the best interest of the "people"
So the most important purpose of the Federal Government is to regulate the republic and maintain law and order and well as democracy for every citizen.
Hope this helps, if you need me to expand please ask!
American colonists felt suppressed and unfairly treated by British rule, so when we broke away from that we shaped our society with the goal of freedom and independence. we did not want to feel like we did under British rule, and we wanted to be and be seen as greater