Ummm... a good question...

It was a branch of the Illuminati defecting from the main illumination boss, the Monarchy of England, so they could build their own country. Remember that there was a war as result... Check Washington DC, the Seal of States, the US$ note, etc... to find all the illuminating symbols.

Then those illuminated took on the task of killing practically all of the aborigines from America.

Now that you mention the United States of America... what do you think of the Secession War or American Civil War? You know, the Confederates trying to secede from the United States of America...