Korea deliberately made the Flu
China is most likely the The Man Behind the Man behind the events relating to HomefrontThe Chinese actually the nation behind North Korea from the start as a revenge against America for its economic woes. It then contacted the North Koreans to unite the south and conquer most of South East Asia for them, defeat Japan (particuarly as revenge in regards to the Second Sino-Japanese War), and so while China is still licking its wounds from the economic downturn, can seize Taiwan and attack India. Really, it's just outsourcing the North Koreans for the job of destroying America.
Iran may be partially involved in the Korean invasion on United StatesRemember the part of the timeline that says Iran and Saudi Arabia fought a nuclear war? Iran won this one and conquered the Middle East so they could blackmail the Europeans in not intervening in the Korean-American war.
Despite Korean propaganda, The Greater Korean Republic most likely invaded Japan as revenge for the Japanese occupation of their homeland in the past rather than protecting their Korean citizens and those with Korean ancestry around the worldIt is most likely the Korean claims of their own people in Japan being attacked and discriminated by the Japanese population and authorities are most likely fabricated. Korea did suffered under Japanese rule for over 40 years until the end of World War II. During the years of Japan's occupation in Korea, the Japanese not only tried to eliminate the Korean culture, but also committed massive genocide against the population. That, along with the controversy of Japan denying their crimes against Korea, it is most likely the Koreans in both North and South Korea have developed a lot of personal hostility and hatred towards Japan to the point that they want to kill 1,000 Japanese for every Korean killed during the Japanese occupation. When Kim Jong-Un manages to reunite North and South Korea, he takes this opportunity to quickly build up the Korean military so they can invade Japan out of sheer revenge. [It is most likely that every single Japanese are dead by the time when the Greater Korean Republic invaded United States judging by the treatment of the occupied local American population.