The United States of America (Or USA) used to make up the Colonies and the Republic until 2051 when a great flood hit the USA which made it split into two separate countries. The USA's way of running things (everyone being free to choose their own destiny) ended and was replaced with the Goverment basically controlling everyone and everything. According to Champion both the Colonies and the Republic's goals were strikingly similar which are being the most powerful nation.
The USA was mentioned in Champion when June went on the Anartican's computer. She was interested about how the US used to be ran as compared to the Republic. It's is unknown if the Colonies and Republic will ever form into one nation again but it is very unlikely due to it's different styles of running goverment. They are however allies due to a treaty the United Nations had Anden Primo and the Colonies Chancellor sign.