The New United States [or simplified as New America] is a rebuilt version of the United States, and was founded and created by Jackson Pearce, who went insane and began hunting down his former friends in the early 2030's.
The New United States was founded in 2032, just after the Wasteland War had ended. The original United States was nuked with War Heads, which hit the US and blew up when they hit major cities, including Washington D.C. and other important cities. This was in 2029.
3 years later, a psychotic Jackson Pearce began gathering a massive army to rebuild the United States. They started by rebuilding San Francisco, which was absolutely devastated. They then rebuilt San Francisco, and moved on to cities like Chicago, Seattle, New York, Boston and others. They then rebuilt Washington D.C. and revamped electricity for Phones, TV's, Gaming Consoles etc. and they improved Electrical Technology, completely rebuilding the United States of America, and renaming it... The New United States.
The New United States has 7 colonies nation-wide, and the flag of America was revamped under Jacks' order.