Do they pose a significant threat to the US in conventional war? No, as I liken it to Hussein's regime and military strength during the Gulf War: significant for the region, but wholly ineffective against modern air-based first-strike tactics and smart munitions. They do have significant amounts of artillery and rockets, with various guided ground-to-ground missiles across the country. These have been in place for many, many years and are generally aimed at South Korea. They pose little threat to the U.S. mainland, but put the entire South Korean country at risk, including the U.S. military bases across the region. If they were to attack South Korea, we would strike back, as they are our allies. Now, if they were to take a less conventional approach, such as smuggling a nuclear device into the U.S., then they may pose a larger risk to the American populace.