First off, here's a map showing how far North Korea's various missile systems can reach. The outermost green circle indicates the range of the Musudan: It includes Japan and South Korea but not Guam or Hawaii and certainly not the U.S. mainland.
The Musudan, though tested, is not thought to be particularly accurate. Still, it could cause some terrible mayhem in South Korea or even Japan if it were launched.
What about the range of the KN-08? Well, here's the thing about that: It sure looks like an intercontinental ballistic missile, and North Korea claims it can reach about 6,000 miles, which puts Los Angeles in range, except that no one knows if it works because it's never been tested. And that means it probably can't hit squat at long range, if it can even take off.
New ICBM models aren't like iPhones; you don't just take them out of the box and expect them to function properly. They have to be rigorously, painstakingly tested. Markus Schiller, an expert in the North Korean military, told Global Security Newswire that it was "totally impossible" for the KN-08 to be operational without tests. Even countries that have successfully built and launched ICMBs before, which North Korea has not, wouldn't expect a new model to work perfectly on the first try. The KN-08 was just unveiled last April in a military parade in Pyongyang and has never been test-launched. Analysts aren't even sure that it's real.
The most bullish analysis of the KN-08's potential threat that I've seen this week, published in the Japanese newspaper Asahi Shimbun, speculated that North Korea had only moved them to the coast so that, in the event of a test launch, they would be less likely to fall onto North Korean soil.
More on North Korea: Is Kim Jong Un being more restrained than we think?