how is china, north korea, and the US like 1984?

Although China's population is subject to heavy government involvement, it is too global to warrant the distinction you are referring to. I don't know how the government runs in N. Korea but I do know it seems like 1984 when examining from the outside. They have a "Dear Leader" which resembles the function of Big Brother. It looks like there is mass conformity to one party. The images we see of North Korea show a very controlled population in all parts of life. I'm not sure how prevalent thought control is but it does seem represent in their propaganda.