News

It's because each distinct sovereign state has its own challenges that can't be solved by one blanket overall federal system. The governing challenges that let's say California has are different from the governing challenges Vermont has.

Colonialism had a lot to do with how the governments were organized, so as each colony developed through authorization from England, they had the freedom to govern themselves within certain limitations from The Crown. Each colony developed similar legislatures, based on bicameralism (upper & lower chamber), governor, and then courts. When the Continental Congress came together they recognized each government equally. So there's solid historical reasoning behind why each state is considered their own country.

There was a huge debate at the beginning of the U.S. that eventually realized a combination of Federalism, and individual State Sovereignty. Initially, the Articles of Confederation left a messy system quite like you describe. Yet each state had their own commerce law, would charge fees to cross borders, etc. That system worked terribly due to the fact there was no strong central authority to resolve state differences, so it was scrapped towards a more federalized system that gave stronger power to a central federal government to solve problems, and still left the states enough legal room to govern themselves...The Constitution.