Germany was spending far more on their military during that time than Britain was. If Britain and France had stepped in earlier, Germany would have been totally unprepared and the war would have ended quickly. Not to mention all of the horrors of the Holocaust that would have been prevented.
If Britain and France had managed to delay the war to "prepare" even more, say a few years, the Luftwaffe would have been dominated by jets, German ballistic missiles would have been longer range and more precise, and they might even have become a nuclear power. I really don't think this is the analogy you're looking for.