That little guy just doesn't know when to quit. Still no one is invading North Korea. The US isn't there to "free" the people. Maybe they do not have enough oil or natural resources in order for them to qualify for freedom.
North Korea might not be having huge deposits of crude oil and natural gas, but they are blessed with trillions of USD worth of rare earth metal deposits (including Cerium, Europium, and Gadolinium). Right now, China is having complete monopoly over the rare earth production, and this is causing problems for the manufacturing units in the United States and Japan. If these deposits can be acquired by the American corporations, then they will be able to make good amounts of profit.