Is it too radical to say that I don't think the United States should have ever interfered with Japan's conquest of Manchuria by placing an oil embargo on that nation and cut off trade with Great Britain until the end of the war? Then the Japanese would have been satisfied with their new imperial territories and Britain may or may not have fallen to German hands. Even so America was already a global military power after the Spanish-American War and was going to be involved in some sort of arms race in the middle of the 20th century no matter if it was the Greater German Reich, Japan or Red China and the Soviet Union. Germany had no chance of winning the war after invading the Soviet Union even it would have lasted until 1947 or 48. Japan would not have been able to keep its assests in China for more than a few decades. All America had to do was maintain a strong national defense and response and it would have really been in no danger. If the US didn't develop the bomb, the Germans certainly were not going to, and the Japanese would not have had the manpower to do so. The Soviet Union maybe in a decade or so, but not triggered by an arms race.