If you want to really prevent taking Pearl you may do 2 things:
1. Get the marines and FTR out
2. Send an Army and AA/2nd Army
All of these can be done without decreasing US mobilization. You may also research Infantry Weapons and AA from the beginning, to enhance these troops. Honolulu is placed on mountain too, it won't be that easy to take. Ultimately, you may try to setup some kind of ambush for Japanese, though I never saw it done seriously. Perhaps other players can share their exp in this regard.
Nevertheless, in my opinion concentrating your effort on protecting Hawaii is really not helping your game, quite opposite. US from the beginning should focus on air and armor techs, to build bombers and tanks. Infantry comes last, so you shouldn't rush IW.
What is more, losing Honolulu is not detrimental to your war effort. It does hurt your National Morale, but nothing gamebreaking. If I remember correctly too, you don't have to own it to win the game. Let the Japanese sit there and protect this soon-to-be liability.
And one thing to mention, up to around mid-1942 Axis forces really can take whatever they want, where they want. But they can't take everything at once. If he is invading Pearl, his invasion of India or Syberia probably won't be that strong. And it takes a lot of $ to send SF's/HQ's and bring them back again, really.
Hope it helps.
< Message edited by Marcinos1985 -- 12/1/2020 9:18:42 PM >