You can’t prep an invasion force of that size without the word getting out, anyway.
REALLY? Ever hear of Normandy?
The Nazis knew the invasion of France was being planned. The Allies just were fortunate enough to deceive them that it would be at Calais.
That was then, this is now. The US was far more unified, the Axis much more separate. The press was mostly patriotic... now it seems to be focused on either the Left party line or short-term advantage. Our government is so shot full of Muslims of questionable loyalty that there are very few secrets.
If my assessment is wrong, I'd be very happy.