Why does the US have militia?

"Allowed to operate."

It's because we're a free nation, although I say that with the awareness that there are forces in the country that are actively trying to take our freedoms away as we speak.

There aren't really very many militia groups in the US and the ones that exist are small, but they at least provide some kind of counter-balance and check on federal power.

By calling attention to a well-regulated militia for the security of the Nation, and the right of each citizen to keep and bear arms, our founding fathers recognized the essentially civilian nature of our economy. Although it is extremely unlikely that the fear of governmental tyranny, which gave rise to the 2nd amendment, will ever be a major danger to our Nation, the amendment still remains an important declaration of our basic military-civilian relationship, in which every citizen must be ready to participate in the defense of his country. For that reason I believe the 2nd Amendment will always be important

In my own native state of Massachusetts, the battle for American freedom was begun by the thousands of farmers and tradesmen who made up the Minute Men — citizens who were ready to defend their liberty at a moment’s notice. Today we need a nation of minute men; citizens who are not only prepared to take up arms, but citizens who regard the preservation of freedom as a basic purpose of their daily life and who are willing to consciously work and sacrifice for that freedom. The cause of liberty, the cause of American, cannot succeed with any lesser effort.

It is this effort and concern which makes up the New Frontier. And it is this effort and concern which will determine the success or failure not only with Administration, but of our nation itself. - President Kennedy