I ended up halving the size of all the divisions defending the Japanese mainland. I originally had a division of 4 infantry brigades on each port. Now there are only 2. I used the manpower from that to build more paratroopers taking my total to around 78 divisions of 5 brigades each (390 Brigades). (Need to double check that I am not 100% certain). I think I only have 2 more divisions in production just now.
Difficulty is normal.
I played through quite a bit last night and got screens but did not have time to write it up. Basically Haiti -> Bermuda -> Florida... Was very good fun, quite epic. LOTS of USA troops but most of them under strength. Some nice encirclements and the first time I have had to retreat paratroopers from a battle that was going sour.
I am very glad there was not much time between DoW and getting troops attacking USA mainland. If all the divisions I faced were 100% strength instead of 25%... I will try to post details and screens tonight.