Unha is actually a satellite launching variant of the Hwasong-13 ICBM. The “satellite launch” was the fifth (the second in a year) test of the Hwasong-13 and the first to succeed. Used as an ICBM the Hwasong-13 has a range of 9,000 kilometers, meaning it can reach the United States. However, it must carry a heavier (than 100 kg) payload to deliver a nuclear weapon. While a nuclear weapon can be built weighing 100 kg (or less), the need for a heavy heat shield (for re-entry into the atmosphere) means the ICBM payload must be 500 kg or more.
The UN has put sanctions on North Korea which forbid the testing of long range ballistic missiles. North Korea’s attempt to get around that by launching a satellite does not work with the UN, and more sanctions are forthcoming. The test is seen as a continuation of the North Korean effort to develop an ICBM that can hit the U.S. with a nuclear weapon. The United States has already deployed an anti-missile system in Alaska, specifically to stop any such North Korean attack. For the North Koreans to launch a successful attack they would need at least a dozen Hwasong-13 missiles and be able to launch them simultaneously. If that happened, one or two might get through. But since the Hwasong-13 is a liquid fueled missile, the lengthy launch preparations would alert the United States, who could then use ICBMs or bombers to destroy the Hwasong-13s before they were ready to go. Thus, as a threat to the United States, the Hwasong-13 is a failure. But the next stage of ICBM development involves using solid fuel rockets, which can be launched without any warning. That is what North Korea is working towards. Ally Iran has made considerable progress in developing large solid fuel rocket motors and that technology would be available to North Korea. Iran got this tech from Pakistan, who got it from China, who got it from Russia, who stole it from the United States.