Maybe said before, but I am too lazy to read all posts.
When D-Day happened the war was already over. As a Dutch man I still am very glad it happened, otherwise the Netherlands, Belgium and France would have the same fate as Hungary or Poland.
I voted battle of Britain. No staging ground for US troops. No Atlantik Wall. Way less soldiers needed to protect the coast. But most importantly: MORALE! The boost to Germans, all resistance movements in France and other countries would have lowest morale possible, Russians fight alone, US not so eager to join the war, less British troops against Japan (or none at all, peace?) etc.
