Oh, the Germans had learned something from WWI, but not the lessons one might have hoped: they learned the importance of tanks in modern warfare, and the basis of blitzkrieg — fusing the tactical innovation that had been turning the tide in their favor before the entry of the U.S. and the first generation of British tanks into the war with the use of tanks. (Though it was really a British captain, B.H. Liddell-Hart, who learned those lessons and set them down fair and square in books, which his own country’s General Staff didn’t read while the German General Staff (and Patton) devoured them.)
What the Germans should have focused on were U-boats ...
Strategists (Monday AM QB's) have said if Nazi Germany had 40 more U-boats ready to deploy by 1940 they would have effectively cut Britain off from supplies ... food, armaments, fuel.
Once the US entered the war in December 1941 it was essentially over for Germany. The US and Canada had a stream of supplies & war equipment, production uninterrupted by bombing, moving across the Atlantic. Very little in the way of German U-boat activity to stop it ... especially the last two years of WWII.