What might have happened if mcarthur had convinced truman to expand the fighting into china? how might today’s world be different?

MacArthur wanted unlimited war and use of bombs on China during the Korean War. 

For the what if, let's try this scenario. MacArthur drops an atomic bomb on China forcing their surrender to the US. The US requires a democratic election and "encourages" the election of a Nationalist hiding out in Taiwan. Nationalists set up a democratic and capitalistic government. They would have tip the balance of powers on the US's side for the Cold War and would have become an industrial powerhouse much sooner. Economic deals would have been created with China in the 1950s instead of the 1970s. More than likely they would have eventually had conflict in the country as communists tried to rise again like has happened in the Middle East to countries we set up in the 1950s and 1960s.