Yes, although not definitively for South Korea.
In an interview with Marie Lu on bookyurt, she gives the following responses:
Byrt: YES. And as for the whole country, you split it east/west?
Marie: I split it down the middle, from the Dakotas through Texas. The west half is called The Republic and the east is called The Colonies – and they hate each other!
Byrt: So were there any historical echoes in this project?
Marie: Definitely. The Eugenics movement that happened in the United States in the early 20th century was a big influence, as well as ancient Sparta and their habit of placing babies that were considered too weak to live out on a hill to die. North Korea was another big influence. It’s fascinating to see in real life how quickly a group of people can be brainwashed by their government, if the government has complete control over everything.
So while it doesn't mention North AND South Korea, it definitely says that North Korea and the government control was an influence in the book.