Had an invasion of Europe been launched before the American forces learned modern warfare, we would have been slaughtered.
It’s true that the US did gain valuable experience in North Africa. But the meatgrinders in Italy and Sicily were not needed beyond the collapse of Rome.
Not to mention, at that earlier time, the Germans had western Europe nearly stripped of troops while fighting for survival in impossible battles in Russia.
The British leaders were an impediment and prolonged the war.