what is the necessity of 50 "states"? why couldn't it just be the "United Country of America"?

Each state is considered to be a country in it's own right.  The federal government was supposed to provide a common currency and national defense.  That is why we have different state laws. 

You ignorance of government is showing.

Because the intent of the Founders was for each state to function independently... basically small, unique countries united under the protective umbrella and support of America where interaction across state borders is necessary. 

Edit:

That's why the Senate only has 2 senators for each state while the House has a proportional representation based on population size of each state. There is nothing unfair about it because each state has totally different issues and interests. If it was based purely on size then the less populated states would be left out in the cold... their opinions going unheard. That is NOT a democratic process. 

Because we are a country composed of 50 sovereign states.  We have a federal, as opposed to a national, government.  This federal government was formed by the the states and the people giving up certain, specific and limited powers that are best accomplished by a government which has overarching powers - defense, trade, postal service, etc.

But the states retained all the power not enumerated to the federal government in the Constitution, and not forbidden them by the same.  Per the 10th Amendment.

This is why the 17th Amendment is the most damaging and harmful change to the Constitution.  The states no longer had a voice in running the federal government.  Since then, the federal government has been on a power binge, usurping states' powers without regard to the Constitution.

Read a history book.

Obviously you never studied history.

When European nations first started coming to America they formed colonies. After the revolutionary war they were no European colonies. So they started using the term State!

Cause it wouldn't really be a free country without States. Go play in the street 

Then you'd never get away with someone losing the election by 2 million votes and still being made President.

read a book. the states were formed one at a time as more and more people came to America. each one had separate autonomy.

51 states you forget Israel